How do I stop trying to be perfect/being a control freak?

Im 16 and last yr made straight As and my weight loss was doing so good. This year its a lot harder for me to lose weight and I dont have straight A's cuz I have a B and I hate Bs cuz there not As. My point is im a perfectionist and I try to control everything and its making me so stessed out and depressed and my self esteem is through the floor and I finally pinpointed it all done to the fact that I feel I need to be perfect. How do I stop so I can actually enjoy my life?