period is super irregular

Ok so I'm super active and I NEVER get my period. I'm a virgin so I'm definitely not pregnant. But I know being really active makes it lighter but does it usually make it stop for months at a time? It used to be super regular and now it's never here. I also got it one time for almost 2 and a half weeks. I went to the doctor and got on a pill and it made me gain weight like crazy so I stopped taking it, and it never set my period back on track. Anybody have/had the same issue??