I want more out of life

I'm writing this while laying in bed, thinking of everything that's been going wrong in my life. I've been dealing with depression and anxiety problems for well over 2 years now and I've been trying to find the cause of it all, but always come up short. I've been mostly thinking of how lonely I am and how everyone seems to ruin anything remotely good that happens in my life. My highschool prom was last weekend and I couldn't help but feel sad when thinking of it because I have trouble talking to people (especially girls) so I didn't have a date and the one time I actually had a "girlfriend" I messed it up because I was afraid of what might happen in the future between us. I saw all of her pictures on Facebook with her new boyfriend and it just made me feel empty inside. I just want things to go back to the way they used to be, back when I didn't worry so much and I wasn't sad all of the time. The better days.