I've gone flying off more horses than I can remember AND gotten run over by a car AND gotten hit in the face with a soccer ball AND had a large tree branch land on me....no brain damage. Sum total of injuries from hitting my head: 2 broken noses, some stitches, a few bad headaches. NO brain damage! You are fine, you just need to stop obsessing. Easier said than done, I know, but a good doctor or therapist can help you through it.