I've heard doggy style is a lot more pleasurable than missionary position, so maybe you can try that. Or go get one of those sex position books from a book store and try out different things and see what feels better for you. As Tyler said, different things feel better/worse for different people. Also, try rubbing your clit during sex, as most women have a very hard time orgasming from just vaginal stimulation alone. Or you could try having him eat you out or finger you beforehand so that you're close to an orgasm, and then have sex, that might make sex better for you, because you'll be more turned on, and more into the experience.