Need advice for dealing with first break up

I know this sounds pathetic but my girlfriend of a whole 8 days (again, I know that sounds pathetic) broke up with me. It was a long distance thing (we met on Tumblr) and she was really nice but slowly I heard less and less from her until she said she wanted to break things off romantically.

Apparently she had been doing some soul searching and came to the conclusion that she was a lesbian and not bi like she previously thought. She says she still wants to be friends but I'm really hurting. This is was my first relationship ever.

I'm a 29 year old bi autistic man with severe hang-ups about my weight and lack of social skills. I was under the impression that I was genuinely unlovable, that this empty void I felt inside me would never go away. The days where she was my girlfriend were some of the happiest I've been, but now that void is back, and it's worse.

What do I do now? How do I stop myself from spiraling out?