i am 19 years old,from past 3 months i am continuously having spotty bleeding but each month, 4 days i got heavy bleeding(as i get during my periods).I already had proper medication from a doctor and had the medication properly it stopped for a while(may be 2-3 days) but,again began,further on i did not consult doctor...

is this the sign of any cancer? I have no pains in abdomen nowhere i am perfectly feeling normal.
but three months is not a small period of time right??