Dumb accident on my end... his fault?? Possible pregnancy?

I don’t believe in the pull out method and condoms are the best for me since I hate birth control. Okay, so I had sex a few weeks ago twice in one night... we started of with condoms and ended up with them. I told him to keep them on but he secretly took both of them off. When I realized that they weren’t on he had already pulled out and came on me. We used a towel to clean up. Before round 2, he promised to buy a plan b because “the condom slipped off” After round two, we used to the same towel. I cleaned myself first, then he wiped off and then I wiped off what was left on me. dumb accident because the towel was wet when it touched my vagina. Touched my inner labia/ vaginal opening..

My periods have always been irregular but the app says that it’s around the time that I start my period (it says it starts today actually, but periods could start any time of day), but I have been cramping, a little nauseated, and had aching boobs. One day I noticed that I had brown discharge when I wiped. A day or two later there was more brown discharge on my pantyliner.

Could it be possible that I got pregnant? I know it was an accident on my end, but it would be his fault for being so sneaky and trustworthy right? I’m 21 and he’s 20. We both stay with our parents. He works a real job, I babysit and volunteer. I know someone is going to say go to the doctor and I will one day this week. I just wanted to post to see if anyone had or is going through something similar.