Why is everyone else happy?

Why is it that everyone else has friends and significant others to turn while I'm in just one unending hell of isolation and loneliness. I feel totally unloved, unable to be a part of any sort of community, like I was born in practically wrong realm of existence. Any social skills I have I only understand in the way you would understand things if you read them from a text book: having an idea about how they work but not the real understanding you have with firsthand experience. I've been called many things: a creeper, a loser, naieve, man-child. It's like for those of you who say you can't fit in, you have no idea what it's like to not be a part of the real world. To feel like everyone else is in on the secret to living in this existence except you. I don't understand the world and I'm tired of being alone. I'm 20, never had a gf, clinically depressed apparently, I have suicidal thoughts but i don't actually want to kill myself (I like imagining the ways I would die and watching people's reactions of horror. I think it has a kind of grotesque beauty to it. A symphony of carnage if you will). God why am I miserable.