Nervous and worried

So me and my boyfriend had unprotected sex a couple weeks ago. We were positive he pulled out in time and knew I shouldn't be worried, but I'm starting to worry. My period has always been irregular (which I am told is normal for dancers, me) and I am not on birth control. It looks like I am 4 days late for my period but I don't know if it's because of my irregular period or if I might be pregnant. I'm so nervous and I don't know what to do. Help