I've tried very best to be cautious and be ready for anything, looking up as much as I can be being safe about any sexual activities. Recently, I was fooling around with my boyfriend and semen got on my stomach. He wiped it off with a tissue, and for an odd reason, absent-mindedly swiped my vaginal area with it. I keep worrying that it could have gotten me pregnant. What are the chances of getting pregnant from that incident?