I'm nineteen, friendless, and have no girlfriend. I'm really depressed...?

Maybe you should try to be friends with different people. It seems that you are stuck amongst a group people who are superficial and their idea of fun is not yours. The only thing you can do is be yourself, hang out with people who don't have depression because negativity hurts the soul or the human spirit or whatever you want to call it. Perhaps just meditate and take away all the emotional baggage, what society thinks of you, what you think of yourself. Just take a moment to not think and just be still. After that how about volunteer and help out others it gives a sense of purpose.