Please answer!

I had sex Sunday the 30th and he came inside of me. We used a condim but I was still worried that some of it may have some out of the top of the condom. The next day I took the plan b pill. Then that Sunday I wike up to some blood in my underwear. There wasn't a ton but enough to to need a pad. There was a lot at first but then barely any. Then it was like it was over. I'm scared that I am pregnant. Should I be worried or what? I just got off of my period on like the 29th or something. I'm not supposed to start again until the 24th. Was it my period, implantation, or side effects? Also if it's implantation how long after taking the pill should I wait to test? I really hope I'm not pregnant.