I am petrified of shots! Help!?

I am 17 years old and I've been petrified of shots my entire life. Anytime I hear that I even MIGHT need to get a shot, a buckle down on my knees and start crying. I start breathing really fast and even get dizzy sometimes. I'm not scared of like sewing needles, or sharp objects, I've gotten my ears and bellyon pierced too. It's just shots that I'm afraid of. I'm not scared of the 'pain' because I know that they don't even hurt that bad. I don't know what I'm scared of! I've tried everything from relaxation techniques to positive reinforcement to not looking, nothing seems to work. It has gotten so extreme that even my doctor dreads telling me I need a shot. I'm 17 years old, I need to figure out what to do! Please help me