i think i am loosing it HELP!!!!!!!

It seems like nothing is wrong but deep down there seriously is. I have no idea what it is. I walk into my house and i can't stand being there i leave as soon as i can. the only person i want to be around is my gf but i don't want to be around her to much to the point where she won't like me anymore. my parent's are fighting and i just choose to ignore that and don't beleive that is bothering me at all. My girlfreind really doesn't show that she likes me that much unless we are alone and she is in a laid back mood, whick this sometimes bothers me. why do i feel so depressed all the time? i try my hardest to be happy, because i am a happy person that enjoys having fun and doing things but it seem like everyday it just get harder and harder, and now i really don't even talk at all. So is there any advice to what is wrong with me? where did my enthusiastic self go? and why do i feel the way i do????? PLEASE HELP if u can