to find your g-spot: check out Atropos4's post up near the top. she's got some good instructions.
as for the other part of that, part of it may just be that you need to relax. Remember, this is all about having fun, right?
If doing a certain thing is what get's you off, try to work that into your sex in different ways. Like, if it's having your clit rubbed, you can show your boyfriend and have him rub it during sex, or many other things. But really, it's all about doing what feels good.