OK, I realise there are a whole load of issues you need to address here, and there's some very good advice from other forum members, but leaving that aside I think the way you approach sex could be altered to help you feel a little more secure, and possibly more confident and sexy into the bargain.
Negotiating sex is a great idea, and really should be done more. Talk before the session about what you're in the mood for, what you'd like done to you and what you'd like to do. Even if you're not into anything particularly kinky, this can let your partner know what kind of mood you're in and hopefully allow you both to pick a speed that you're equally happy with. Try using phrases like, "I'd really like to..." "Please could you..." "Could I please..." "I'd love to..." "Maybe you could..." "...if that's OK" "...if you'd like to" "...if you're in the mood".
Having even a quick conversation like this will let both of you know what to expect. It's not a contract, but it does show your intent and let the other person agree in principle to what's about to happen. If things then change, you can at least both acknowledge that you're re-negotiating what you're both comfortable with - it's not just a case of guessing and mis-interpreting the other person's mood. Also, if either of you later says that they didn't enjoy what happened, you can deal with that sensibly without throwing blame around, so long as you stuck to what you had discussed.
Needless to say, communication during sex is pretty damn important too. Even making the right noises if you can't string a sentence together...
This kind of verbal foreplay is not a million miles away from the sort of thing recommended in the "How to be Dominant" blog entry. A subtle shift in emphasis and a little more confidence, and your negotiation becomes "guess what I'm going to do to you, you lucky girl..." Don't forget you're still negotiating, but if you get a feel for what your partner enjoys most then you should be able to start with those kinds of suggestions pretty confident they'll eagerly say yes.
Hope this gives you some ideas, and that it helps you to move forward more confidently. From your original post, your OH sounds like she would be happy to try, at least.