What causes recurrent heavy nosebleeds?

Different causes. Nose bleed reasons: nasal congestion or nasal dryness, ^ blood pressure, excessive use of decongestants, being at ^ altitude, trauma to nose, nose picking, or blowing the nose hard. Bacterial ; viral infections can ^ risk as well as bleeding disorders. Recurrent nose bleeds may be due to broken vessel in the nose. Alcohol / Cocaine abuse can cause nose bleeds, as can tumors.
Variable. Could be recurrent habit i.e. Nose picking , or fragile blood vessels on the mucosa , or could be problems with blood itself ( bleeders) etc. Start by avoiding the bad habit, then go to see pmd or ENT to have further discussion and evaluation. If needed, your primary care doctor can refer you to see a hematologist if your doctor thinks you may be a bleeder.