My last period ended on May 2nd and I had unprotected sex two days after, pregnant?

My last period ended on May 2nd and I had unprotected sex two days after. We didn't do it for longer than a few minutes on and off. He didn't cum. And he told me he did not feel the sensation of precumming as well. But we had sex beforehand and he assured me there was no left over cum on his penis and that the sperm should've been dead by then, being exposed to air. But I found that I was brown spotting last night May 10th as well as the next morning.

I'm not sure whether or not I'm pregnant, because I have also been stressing this week on other matters like finals as well as last night I have been stressing on receiving an online order in time for an event; that could be the cause of it. And this could also be dead blood as well. But before, I usually had brown spotting a week or so before my period. But this one is different, I started spotting way too early and my next one doesn't arrive until the next 3 weeks.

I'm just really worried about this irregularity. I'm not sure whether or not I'm reading too into this. I know this is quite early to be asking such questions, but I'm really worried.