Less than three days ago, my boyfriend and I were fooling around. After he ejaculated he fingered me. Although we are confident there wasn't any sperm on his hands, I know that if there was and his hands were near my vagina then there's a chance I could get pregnant. I should have been past ovulation, which I know decreases the chance of pregnancy, but I can also be irregular by a week or two, so I'm not certain if I was ovulating or not. Is Plan B something I should take just to be certain?