Late Period

My boyfriend and I have recently started having sex. He was the first person I’ve had sex with. We have done it several times now over the last 2 weeks. We have always used a condom because I am not on birth control yet. I realized after the fact that I lost my virginity the same time I was ovulating. I was supposed to start my period yesterday and I have not started yet. I am supposed to start birth control Sunday but my doc also said to let my period happen a bit first then take it. Now that my period is late idk what to do. We’ve never had issues with the condom so idk how possible pregnancy is but I also have very regular periods. I don’t feel like I’ve been stressed or anything but I didn’t know if having sex has changed my hormones therefore affecting my cycle. Any thoughts or ideas would be appreciated thanks!