Irregular Cycle, Please Help!!

My period is really unreliable, for lack of a better term.

- I’m not sexual active and never have been (I’m 19 if that matters)

- I don’t feel any pain or sickness of any kind

- I’m not taking any medicine atm (I took birth control at 16 and stopped but these issues are all recent)

There are times when I could go a month or two without a period. I can’t even remember when my last one was, but I know it wasn’t to long ago. Is this normal? Am I infertile now? What should I do?