You can not get pregnant if, when fooling around with your boyfriend you touch a wet spot on his jeans (that might be semen… or vaginal secretions… or spilled cola…) and then go to the bathroom and use that hand to hold the toilet paper that you wipe yourself with.
For that matter, you can also not get pregnant if, when fooling around with your boyfriend he actually ejaculates on your hand and then you go to the bathroom, pee, and hold your toilet paper in that hand while wiping yourself. Still, in that case I’d wash my hands first. Sticky. Yuck.
See the explanation from #4 for why you can not get pregnant by touching semen and then going to the bathroom. You can, of course, get pregnant from touching seamen and then going to the bathroom and having sex with them… but that’s an entirely different story.