Nausea, why can't you be butterflies?

Hey everybody, I've got a relationship advice question/rant. It's very pressing for me at the moment.

Always when I start to be intimate with somebody, or there's even just the realistic possibility, I pass into this physical state where I'm a bit nauseous or my tummy aches, food tastes like paper maché, I can't sleep well (usually sleep like a baby) and I'm sort of dizzy and unfocused. I'd love to say it's just being in love, but the problem is that during this time - like right now - I feel really insecure about whether I really like that person or if I want to continue getting closer to them.
I'm not talking about relationships that start out with sex here. It's usually people that I've been friends with for quite some time.
I think part of it is nerves... me being afraid of the closeness, of letting people into my personal space. I can never initiate this, only react, even though consent is very important to me and all the partners I've had. I guess I'm scared that I'm not good enough, but why do I only get like this with sexual relationships, while I'm really comfortable entering close emotional commitments with people?

I'm going through this at the moment, and I try to solve the "do-I-want-this?"-thing by looking at my feelings for that person before I knew sex would happen. Ok, I think I wanted it, but why can't I see that now? Why am I all nerves and almost no happiness? I know it's going to pass, but I don't want to feel this NOW.
Has somebody felt something like that? :help:

PS: and don't say it's because I'm trans, because duh... I already know that and it still doesn't make sense to me :dry:

 

Thanks for the advice! Hmnah, it's not about nerves before sex or being or talking with her. I actually get calmer then, I'm just worried and different all the rest of these days. I guess I'm so hesitant to cross that line with anybody, even though I also want it?