is spotting because of the pill?? or pms?? or pregnancy?? 😫😭

Okay so I started taking the pill this month, and I'm currently half way through the third week of the pack. I've been having brownish discharge/spotting the past two days. I'm pretty good about taking my pill everyday at the same time, but I also did have unprotected sex only a few days after starting the pill (he pulled out, I know it's not the best but at least he didn't cum in me lol)... should I be worried about being pregnant or is the spotting just a side effect of birth control??? should I just relax and wait for my period to come next week??