I'm still a virgin, never officially had intercourse of any kind, but recently tried something with my ex. I wore a pair of panties he had came into about an hour previously. They also had dried cum in them from days before. It was all mostly absorbed into the fabric but was still wet on me down there. We are no longer together and the more I think about it the more I'm concerned about an STI. Can you contract an STI though sitting on old absorbed semen?