I told my doctor that my period be off and on?

well she told me that dont worry it must run in my family. are i am a person with an on and off period i dont understand i will be bleeding for thee months and sometimes i will miss like two months. and i ask her for some kind of medican but she said once agin i am a person with and on and off period. i dont understand i never took no birth control are nothing. and i told her when me and my boyfriend have incourse i bleed and she told me once agin theirs nothing wrong.