What Causes Hair Fall On Massaging Minoxidil Onto The Scalp?

Hi , I am a 21 year old male . I have been experiencing sudden hair fall . When I consulted a doctor he said it was androgenic as my father is also bald but that baldness is setting in faster than normal so prescribed minoxidil and amexidil. When i used minoxidil for the first time and massaged the foam into the scalp lot of hair came out around 25-30 .Should i be worried ?