Pleas help!!

Back in December of 2016 i started taking birth control on and off then i finally stopped in March of 2017 every since then i been having irregular periods, at first it would come every 2 months and then stay a month now it’s like it comes for almost 2 months and then i be off for a week or so or when i have rough sex it brings it back... me and my fiancé are trying for a baby and this is really frustrating we can’t even have sex because I’m always on my cycle.. i want to try Pre-Seed but will that work ? If I’m having periods for so long? Am i even ovulating? I’m so frustrated i want a baby so bad this year