Am I pregnant?

About a month ago my boyfriend and I had unprotected sex which was not the best idea. He pulled out and we were both sure that nothing happened. The next day I got my period and now this month my period is a couple days late and i have been having very short cramps. It's not unusual for my period to be irregular but i've been paranoid and stressed since we did it. i'm young and neither of us are ready for a baby. I've been slightly nauseous at random times, but i haven't thrown up. I'm worried that i'm confusing signs of my period coming for a possible pregnancy. I have not taken any tests yet and I want some feedback. Thank you!