Genetic androgenic alopecia can start with puberty so you may be seeing early signs. You need to see a doctor for an exam if you want a diagnosis. There is no way to completely stop genetic hair loss.
Many times using Minoxidil just by itself doesn’t regrow much if any hair. Used with Finasteride your chances would increase a bit. Both are used primarily as defenses to help slow down the loss. Hair transplants are what actually make a noticeable difference that most patients are looking for.
You generally cannot "stop" genetic hair loss. There are medical and surgical treatment options but these are not "cures". You first need to see a doctor for an exam and establish a treatment plan.