Why do I feel so upset when certain friends hug me?

Okay. I’ll try to make this not confusing. It’s really confusing to me.

Recently, I’ve been feeling pretty much alone. I’m usually surrounded by people, but I’m not very social. So I always like receiving some form of affection from a friend, or know that they still care. but lately, whenever I meet one of those people and they give me a hug and say goodbye, I feel like utter crap afterward. Like I miss them so much already when we’re only walking away from each other, and (for some reason) I feel like an idiot. Then I start to cry. Even though they were happy to see me, and I was happy to see them. And it’s only been with a few of my guy friends I like (not crush-like, but generally-like, and admire a lot). When I hug guy friends that I am currently crushing on, I just feel butterflies, not this crappy, depressed feeling. Just remembering this stuff makes me cry sometimes. Ughhh.

Is it just my crazy hormones (um yeah I’m 16, by the way)? Or is it because I’m so detached from everyone that a simple hug from a friend chokes me up? But why is it only these guy friends?