Could you help me with my life?

I dunno whats happening anymore. I am only 15, but I am always stressed, feeling down, angry, lonely and am always full of heartache. I have friends at school who try to make me feel better but it never works. I have been this way ever since I moved away from my dad. I left him behind coz he was becoming abusive and I had to leave for my own safety. But i left behind my best friend also. These make me feel sad and angry. I am stressed because of the amount of pressure I am under at school. Lonely because I have nobody to talk to about this as my parents don't really care. Heartache because I wanna get somewhere in life, you know for a sport or something, its my dream and I don't wanna give it up but i think i have to because i am sure I can't make it with all of these emotions and lack of energy. I have been to counsellors and doctors, they say I am not depressed but i dunno... I have a horse and I never get to see him, and he's pretty much my only friend at the moment... I always feel down because I know what the future holds for me... and that is nothing.... I wanna be a professional swimmer or something but i am pretty ure I can't get to this goal and it makes me sad coz thats my dream.... Please give me some advice on what to do... Thankyou for your input if you do :)