when you get naked hump the air a little shake your penis to help hold erections
Take it easier. Get naked with them WITHOUT any intention of having sex. Tell her you're NOT going to have sex and just give her a naked massage instead. If sex happens, let it, but don't make intercourse the issue.
You're setting yourself up for failure if that's what you're looking to do. Take away the motivation for sex and make it about touch instead.
I know, from a male perspective, it seems pretty wimpy, and "*******" is great, but the psychological aspect is important, too, and you need to handle that, too.
-Bill