I guess... I need help...

I've tried to deal with it my own way, but I guess I have to seek help now... For all my life I remember being bullied... For being pale, for being skinny, for my insecurities. Just lame stuff like that. I don't remember lashing back or anything, I just got very upset and sometimes cried... Then the made fun of me for crying. I felt some kind of sadness, but not too bad... It was a horrible experience, fearing every day at school, fearing attacks both physically and verbally.
Fast forward to a closer date: Life wasn't too bad, things had really looked up. Until the start of a new term at school; I felt the hatred burning inside me as more of a frustration then a sadness. Why did they have to do this to me?! Some donkey took my glasses and threatened to break them one day, and I took him by the neck and wouldn't let go... It was like I had no control... I was a spectator... Although the rush was enough to relieve my anger. A few days later, some other c*** was putting my phone number everywhere, around the school and on the internet, and my parents already had enough prank calls and they didn't think highly of my friends (although it wasn't them). I felt a heat in my face, I was shaking and I felt confused once more. Eventually I walked up the person in question, punched him in the face, and as he attempted to retaliate by kicking me, I grabbed his leg and threw him the width of the room... After this, I realised what I had done, ran off and cried... I felt so bad...
I know this is not a very good way to deal with anger, so I attempted to keep it bottled up, but now, I bite peoples heads off all the time. Whenever somebody does something wrong, I just get really angry with them, shout at them and sometimes physically abuse them... I feel that I can't count on anybody for anything, and I want to stop hurting my friends when they make mistakes... They are good friends for putting up with me and I guess they know that I used to get/still do get bullied a lot. I just feel that there is no way to safely relieve anger, and that I have to get my revenge on other people who are so horrible to me. And showing sadness like crying is a weakness...