What is happening to my hair? I’m only 21 years old (with photos).

You are most likely developing balding from genetic hair loss.  There are two wonderful drug for treating this problem, (1) finasteride which might reverse the loss if you are in your early 30s, and (2) Minoxidil plus taking the finasteride pill. You must see a doctor for the finasteride. Whatever you do, do not get a hair transplant until you are at least 25 years old.