When I was just kid I had bloody nose, now I am 21, still have bloody nose, how do I prevent it? Sometimes won't stop for10-20min (iam firstaid certifi

See a Physician. I hope by now that you have seen your md. Repeated blooding from the nose all these years would raise concerns to your physician. In addition to a close inspection by an ear nose and throat specialist (ent), your md would likely want to check your blood count (specifically your platelet count), and your coagulation tests known as pt, inr, and ptt. Check for hemophilia as well. Stay off aspirin!
Anatomy. See :https://www.Healthtap.Com/user_questions/49740 you may also have a deviated septum causing the bleeding... See your local ent.