Another thing about your heart racing as you get towards being sexual?

Is that because you're worried about your performance or a personal issue? Is that because you feel that you are using her for sex? Or that she might think that you are using her for sex?

She wants sex as much as you do, and she gets as much if not more pleasure from it, so you are infact doing her a good thing. You're not taking anything or getting anything out of her you are just enjoying something with her that you both would want.