Dealing with major stress?

I'm a teenage guy that has been dealing with major stress to the point where it's effecting my mind...I have becoming spontaneously angry at times, fighting angry, snappy,super depressed,there have been times when I have had homicidal/suicidal thoughts,sometimes I get so angry that I start to shake and get headaches...am I crazy? have I lost my mind? I think that I am going to start drinking or smoking.....and I know that I should go see a doctor, but I have a great reputation and my situation is kinda embarring....someone please help me..