Dear Pryncess
i know what you are going through. i am also 15 and have exactly the same problem. i too had times where i felt completely worthless and unloved except for the rare times where i hung out with the boys i knew.
There was a time where i was so depressed i had no idea what to do. i would be at school and then just randomly break out in tears. i knew i couldn't talk to my parents bout it cause i knew they wouldn't understand
However, when things were at its worst i couldn't take it and i got extremely bad. Thats when my friend started taking me to her 'shrink' lessons and before too long i started going there on my own. I had that privacy from my parents too as it was during and at school. The person i have been seeing has helped me through alot and i suggest you should see someone about the way you are feeling.
i hope you get so much better.