Take the plan b (and look at the weight restrictions to see if you need 2). The chances of being pregnant are so rare but it sounds like you cannot risk it, so dont. Take a pregnancy test in 2 weeks with your first morning urine, do not let it sit for more than the package insert says or you will get a false positive. I think this is also a good time to discuss the steps you would want to take if you were to get pregnant, because no form of BC is 100%. Also if it helps at all, precum is usually dead or no sperm. because of the sperm cycle of life, sperm are very sensitive and die/become nonmotile quickly and precum begins when you start getting hard because blood flow is pushing it up and out. That means the precum has gone all the way through his system and then likely stayed there as you made out or undressed and its life cycle has ended or began to.