Crush on best friend

Ugh, I need to get this out somewhere...

We've been friends for almost a decade now. We've shared everything together. I've always viewed her as a sister, so I was shocked when I started to have feelings late last year (November I think?) and I repressed them until now, not wanting to admit them.

She has never been attracted to anyone of either gender, which is why I kept it to myself. However, several weeks ago she has re-questioned herself and is definitely interested in women now.

I was excited, but I didn't want to say anything to her since her own questioning would make it overwhelming.

However, a few days ago she started talking about her interest in dating girls. She told me about a girl that she considered asking out although it didn't seem like it was a genuine attraction or a want for a relationship with her. She described it as wanting to know what an actual date feels like, "just to say she experienced it".

I started to feel jealous (although I didn't state this) so I ended up confessing attraction in the moment to see if I had a chance at all. She was shocked, and stated she needed time to think about this. She still wasn't sure about her feelings and didn't want to hurt me, but she also talked about the possibility of us as a couple and a wish to "accept my feelings" since her emotional attachment to me has been there longer.

I feel stupid because I feel like I confessed prematurely, but I was also afraid to lose her to someone else without even knowing if we had a chance at all.

I can deal with a plain "no" and just move on, but the fact she hasn't decided on an answer is making me feel beyond anxious. I can't sleep at all and I can't eat without wanting to throw up. I considered calling her later tonight, but I'm hesitant for obvious reasons.

I think I've done all I can do, how the hell do you deal with this kind of anxiety and worry though? I've never had such strong feelings for someone and I'm afraid of losing the only person that I trusted enough and had fun with as a friend. I can't stop crying even though it makes no sense since nothing bad has even happened yet.