Yes, it sounds like you are going too fast and you are not giving her enough foreplay to get ready for intercourse. Guys can go from no arousal to completely aroused in 30-60 seconds; girls take 30-60 minutes. How much foreplay are you giving her? It doesn't sound like it is a lot. Foreplay, which includes caressing non-sexual parts of the body, is absolutely needed for a woman to enjoy sex without pain. Yes, there are times that a woman is just aroused already and wants to be (excuse the language) "fucked like an animal." However, that's rare and infrequent. If you want to learn to pace yourself, try this: tell her that you still want sex with her, but at her pace and that she needs to decide what you want her to do. If she wants oral sex for 15-30 minutes, then go down on her. If she wants you to kiss every part of her body, then start at the toes and work up from there. If she wants a body massage, then get out the baby oil and give her one (btw, a good one takes about an hour or longer). If she wants to learn how your body reacts to her attentions, then lie down and let her explore. There's a lot more to foreplay than just kissing, breast fondling, and rubbing her pussy a few minutes. That's all it takes for a guy, sure, but maybe the key is to let her show you how she wants sex to proceed so that you both know how to pleasure and please each other.

last I checked breasts are apart of a woman's sex organs..so..I dunno if this will hurt as a suggestion but have you ever tried having her lay down on the bed spreading her legs open while you guide your dick and balls into her? just a thought O: hmm