Here are a couple suggestions: 1) she may not know how - buy a couple dirty erotica books to read in bed or how-to sex books and say you are interested in being a better lover and thought you could read the books together in bed. 2) she may have low self esteem - give positive feedback on any little thing she does do to show appreciation, tell her why you think she is beautiful, ask her what she would like to do on a Saturday and do anything she wants all day. Take some photographs of her. Surprise her with something that she really loves like a new book, a movie, a new yoga mat, whatever she likes. Make her feel special as an individual. 3) she may need some ideas and encouragement - rent some videos that have hot sex scenes, doesn't have to be porno, and say - it turns me on how she is doing that do you think we could try that someday? if your girlfiriend is into porno, then you could play a game where you watch a movie and role play and do the same things that are in the movie. It might help to let her pick out the movie, since I know different women have very different tastes. NOTE - don't try this suggestion if your girlfriend is extremely jealous. 4) she may be lazy or self-centered - find a new girlfriend.

Try to figure out if she'd rather do it in a different time of day. I have friends where she's ready to go half an hour after dinner, but when she gets sleepy and ready for bed THEN he's wanting it. He said that he usually ends up doing the work too, which she appreicates, but doesn't contribute much to. If you can get her actively wanting you instead of passively, even if you still have to initiate, it shouldn't be too much to roll her on top. She might not realize that you're unhappy. Offer her the upper hand as if you're doing it for HER, not as if you're tired of working the same set of muscles and it's time for her work out.

I can speak from your girlfriend's point of view.. she might feel a little self conscience. make her feel completely comfortable with herself by telling her how beautiful and sexy she is. the more confidence she has, the more she will show you her crazy side in bed. also, if you are always the one who instigates. let her instigate it for a change. turn her on a little, then go and do something else like the dishes or something. she will come crawling back for more ;)

ask her since she's so incredibly sexy, y she's so modest in the bedroom...(ego booster) usually this is a self conscience thing, not a selfish thing