Well you're 16 dude you shouldn't be crying every time you get upset. He is probabaly just annoyed because you can't control your emotions sometimes.
Either way he sounds like he doesn't care too much about you. If you were my girlfriend in theory then I would address the issue directly and not ignore it. If you kept crying after my attempts to help you out with it then I would most likely leave you because we wouldn't be compatible.
Him walking away every time things gets heated is a bitch move. I think a man in a relationship should know what buttons to press and how to control the conversations that he has with his girlfriend during heated discussions.
That's some childish shit. Adults stick around and work out their arguments. You don't just take off every time your partner does something you don't like. I'd let him know that's not acceptable before it becomes a habit.