What's wrong with me?

Ok so I'm 14 I have recently started felling as if I don't exsist I have very low energy , I did have a really bad diet but a few weeks I have been eating really healthly , but it hasn't solved it , I also feel awkward round people like I hate sitting at the front or middle cause if someone laughs I feel it is directed at me I always have to sit on the back row where no one can see me , I am also really nervous round guys , all the guys at my primary school hated me the picked on me alot now I am really nervous around them. I don't tlk to my dad very often and my mum critisises everything that I do , we often hv arguments , and me and my brother hate each other whenever he's rude I defend myself by being rude back I cnt help it then I get in trouble. Just cause he plays for a famous footbal team he has loads of awards he gets all the attention. I only really feel at home with my animals I love them so much. I have been bullied for most of my life , threatening to stab myself several times , I feel like Im not learning anything , I regurly cry alot like a toddler and I hate it , my mum thinks I should see I phyciatrist but I will only tell her about how I hate my family. I feel depressed I push away my friends cause I feel they don't care they don't understand what I go through if the don't tlk to me I feel depressed . One minuete i'm happy the next I'm hitting my head against the door in an attempt to knock myself out :/