Go see a doctor and get tested for STDs.

Pain from intercourse can start from one or several possible origins. Sometimes the underlying problem is due to the tightness of the muscles that make up the vagina itself. The vagina is a collapsed hollow tube made of muscle. Often, muscle tightening of the vagina itself is combined with extra tightness of the muscles around the vaginal opening, both just under the level of the lips or labia, and also deeper around the base of the bladder. These surrounding muscles are the ones women can tighten when trying not to pass urine or gas. The name for over-tightness of these muscles is vaginismus. When muscle tightness has been present for a long time, over many years, sore spots can develop around the edge of the opening of the vagina, just where the hymen attaches to the internal lips or labia. The area between the internal lips is called the vestibule, and when these sites are sore. This condition is called vestibulitis. More severe vestibulitis feels like a burning discomfort on a day-to-day basis, usually much worse around a woman's menstrual cycle. This burning of the vulva is called vulvodynia. Vestibulitis also results in a burning sensation from the partner's semen when he ejaculates inside her vagina. Also, she may sense burning when she urinates after intercourse. Very rarely, a woman is born with, or develops, a tissue structure that makes entrance by the penis impossible. For instance, the hymen may be made of tissue that doesn't stretch. Women who can have intercourse, but with pain, may well have problems with the vagina itself, not just the opening, or even with more internal structures. Infection or lack of estrogen might be involved, and it's important to have this checked by a physician. Another common reason is simply that the woman is not aroused when intercourse is occurring and the vagina is not sufficiently enlarged or lubricated. This causes the movement of the penis to become more and more uncomfortable. Deeper pains felt in the abdomen with deep thrusting should be checked out by the family doctor or gynecologist. The cause could depend on whether your friend is experiencing the burning at the opening of the vagina or actually inside the vagina. If it is at the opening that she is feeling the burning, it could be something such as vulvodynia which is when part of the vulva becomes overly inflamed. If the burning is on the inside of the vagina, it could be that she has a yeast infection. A lot of the time you may not know when you have a yeast infection and it is only when you have intercourse that symptoms become more apparent. There are several reasons why women might experience pain, discomfort or burning during or after sex. Sometimes discomfort or irritation is caused by lots of friction during sex - using a lubricant can help to reduce friction and make intercourse feel more comfortable and pleasurable. Other times women experience vaginal irritation during or after sex due to a hypersensitivity to condoms, the lubricants on the condoms, spermicidal lubricant on condoms, or spermicidal jellies. An ingredient in most spermicides - call nonoxynol 9 (or “N9″ for short) - can be particularly irritating to women’s genital vagina's. It may even be that you can reduce the pain somewhat if you try positions (such as Woman on Top) that give you more control over penetration so that you can be more gentle or stop altogether if it starts to hurt. All that said, about 10-15% of women have more complex issues related to vulvovaginal pain - sometimes pain or discomfort may be related to a genital skin disorder such as lichen sclerosus (typically with LS the genital skin gets white in some areas, and your vulva may itch quite a bit); other times the pain may be related to a pain condition such as vulvodynia. For more information about female genital pain - even if it’s not related to pain during sex (some women have pain even when they are sitting in their car) Pain or discomfort during sexual intercourse or vaginal penetration may be caused by several conditions including: Vaginal Infection Certain vaginal infections such as vaginal yeast infections and trichomoniasis are often present without noticeable symptoms. However during sexual intercourse, the rubbing motion of the penis against the vagina and genitalia sometimes causes the symptoms of these vaginal infections to intensify causing stinging and burning. Genital herpes sores are another frequent cause of pain during sex. Vaginal Irritation Many products contain irritants which can cause vaginal irritation leading to discomfort or pain during vaginal sexual intercourse. These include: Any contraceptive foams, creams, or jellies Allergic reactions to condoms, diaphragms, or latex gloves Vaginal deodorant sprays Scented tampons Deodorant soaps Laundry detergents in sensitive individuals Excessive vaginal douching Vaginal Dryness Normal vaginal lubrication is a given for most women; however, during certain times the vagina may be dry and make vaginal penetration painful. Lack of vaginal lubrication can be caused by several factors including: Trying to achieve vaginal penetration to fast before enough stimulation has occurred to allow normal vaginal lubrication to take place; Feeling nervous or tense about the sexual experience can slow down the release of vaginal lubrication; Using a condom may make vaginal intercourse difficult without the addition of a vaginal lubricant such as AstroGlide, K-Y Jelly, and other products. Saliva is an acceptable for vaginal lubrication; however, never use a petroleum-based product such as Vaseline (petroleum products can cause deterioration of condoms and also may create a breeding ground for vaginal infections) Hormonal imbalance during menopause or the years preceding menopause can cause vaginal dryness, as can hormonal imbalance following childbirth. This hormonal imbalance is caused by a decrease in normal estrogen levels which can cause the walls of the vagina to become dry. Women experiencing vaginal dryness for these reasons should use one of the vaginal lubrication methods listed above. Women in menopause with severe vaginal dryness should talk to their health care provider about a prescribed estrogen cream to be used vaginally. Vaginal Tightness Occasionally this happens when you feel tense, or are not fully relaxed when penetration occurs. Difficulty penetrating a tight vagina can happen even when vaginal lubrication is not a problem. Often, the first few times you engage in sexual intercourse, the vagina may be tight due to an unstretched hymen and cause pain at the time of penetration. Sometimes a more severe condition called vaginismus is responsible for vaginal tightness; women with vaginismus experience strong, involuntary muscle spasms of the vaginal muscles during sexual intercourse or vaginal penetration by any object including fingers and tampons. Pain of the Clitoris The clitoris is the most sensitive part of the female genitalia. Gentle touching or rubbing of the clitoris is extremely pleasurable for some women, while for others it is unbearably painful. Clitoral pain may also occur due to poor hygiene; vaginal secretions may collect under the clitoral hood and if not carefully washed away may lead to pain. Pelvic Pain Occasionally a women will experience pelvic pain upon deep, thrusting penetration. Many conditions may cause this pain including: Tears in the ligaments that support the uterus (causes include problems during childbirth, inappropriately performed abortion, previous violent sexual intercourse or rape) Cervical, uterine, or tubal infections such as pelvic inflammatory disease (PID) Pelvic adhesion's (often the result of previous pelvic surgery or PID) Endometriosis Ovarian cysts Uterine Fibroid Tumors Vulvodynia Vulvodynia is a painful, and often hard to diagnose, chronic condition that causes a burning and/or stinging sensation of the vulva and vagina. Having sex should be pleasurable if it's not, tell your partner that you are experiencing pain or discomfort, and see your health care provider for diagnosis and treatment.