Plan B?

So I had unprotected sex and he pulled out and came onto the side of my butt but I have a feeling some dripped down onto my vagina? I’m not 100% sure and yes I’m on BC but the only reason I’m worried is because I haven’t been taking it exactly at the same time every day the last few days, it’s been like a 3 hour time difference. I went to pee after and I was just feeling around to see if I felt any cum and I felt something wet but I’m not sure if it was just pee or cum. I know not the best image but I’m worried and don’t know if plan B is necessary or not. Please help!