Roy
Most men of all ages get erections frequently during the day and always at night. A lot of males will drip out large amounts of precum and even semen when erect. Erections happen even without any sexual stimulation in men frequently. If you want his underwear free of semen then just make sure his balls are emptied out by you or him as often as possible and that will reduce the precum and semen in his underwear. He wouldn't accuse you of having an affair just because females leak vaginal fluids frequently in non sexual situations. Sex organs leak to let off extra pressure and get rid of old fluids building up inside them. Spend your time emptying his balls, not snooping in his dirty laundry lady.
Thank you I actually asked my partner if he watched porn at work he got very defensive but more likely because i ask alot of quiestions about porn he is not comfy talking about it i didnt think he got a hard on or anything but for some reason there was marks in is pants which hasnt happened for a little while now ready this helped thanks