How can I not be scared to fight?

Hey everyone! Please I need help! I have been doing jiu jitsu and muay thai for 6 months now. When I train with pads and heavy bags, everyone and even myself know I am pretty good. But the problem is when it comes to sparring or a real fight at school or something, I feel like I forget EVERYTHING! and I am scared to get hit and I flinch to much. How can This fear go away? Basically how can I stop being scared? I am 16 years old.