Spotting..HELP

So I had sex July 5th and he pulled out but I saw that the condom had broken. I had sex at 2-3pm and I took a plan b at 10pm just to be safe. I had ended my period 2 days before July 5th and had 5 more days until I became fertile. My stomach hurted for a while I'm guessing because of the pill and then today I wake up right now and I have spotting on my underwear it's sorta brown but then a little blood. I always get this sometimes and I know it's old blood but I'm just paranoid because I don't want to be pregnant. I'm supposed to start being fertile tomorrow. Is this fine?? I feel like it's just old blood