Bleeding after fingering?

Jessica

So earlier me and my boyfriend had sex. Everything was fine during sex and was normal. A little while later we started kissing again and whatnot, he fingered me and ate me out but that was it, we didn't have sex again. It felt really good at the time but now I'm realizing I'm bleeding lightly. I'm on the pill and my period is supposed to start next Sunday so it shouldn't be that. What could be the reason for this?