I'd like to join Sophie_M in welcoming you here -she does give good advice and her links are excellent.
I guess there is a lot to feel encouraged about, even though at present things are frightening and seem to have no reason. To know one is likely to lose control is very scary indeed.
The first thing is it has been year, not you whole life, so there is a cause that changed -and of course may be changed beck if treated properly
The second thing is you basically sensible, value your relationships, and understand there is something wrong, you do not just write it off as bad temper but realise such over the top behavior is a real problem.
Third you have take the first step in getting matter made better, by coming here. That in itself must have been very daunting. But that is behind you now.
I would expect the Kids Help Line chat or any of the other links may say to you that you might need some medical help at the moment. I did and once it was under way matters improved a lot. Before I simply go worse.
Do you think you can ask your family to take you to a GP to say what has been happening and see if you can be diagnosed, either for somethng physical or psychological? Once the problem is known the correct treated can begin.
Do you think that's a plan?