I need help

Me and my boyfriend have sex obviously. But I have yet to start to my period and it's worrying the shit out of me. We've always had sex with condom and when he's about to cum he pulls out. But I know nothing is guarentee and I don't know what to do. It's been a month today since the last one and my periods are irregular from twice a month to the beginning of one month to the end of the next month... just any advice... or don't worry would be appreciated