Re: how much is to much
How much did she enjoy it when you were having sex? It sounds like you need to talk to each other better, because you should know why she doesn't enjoy sex more. From here, it's easy to imagine it's something about what you're doing, but you'll need to talk to her to determine that for yourself.
Of course I don't know if this may be part of your problem or not, but a lot of men think sex is supposed to be like porn--just slamming into someone roughly. That's not appealing to the majority of women (at least that I know).