Every body's reaction is different. It is not unnormal to suffer from a period or occasional spotting. Since the depo shot injects you with a hormone which tricks your body into thinking it pregnant it is also extremely common not to have a period at all. I was exactly like the other ladies who did not bleed for a number of years. I seemed to suffer from manic depression. Unlike the pill the depo shot consists of only 1 hormone which effects everone's mental health & physical chemistry differently.
I continued taking it for the soul reason of the absence of blood. Other than that there is nothing positive about it. Everyone I have ever spoken to regrets that shot. & when you finally decide to get off of it, that is an episode in itself. I dont want to scare or worry you, but since you havent been on it for too long your body has not gotten so accustomed to it. Withdrawl shouldnt be so bad for you. Try the patch; you change it weekly, but it's side effects are minimal.