His jeans were wet and ...Am I pregnant

It's very unlikely that you would be pregnant. It is more likely that your period is late because of stress of exams and now stressing about this. Stress can cause the body to function in different ways. I know from past experience that stress can actually stop your period coming for 2 months or so - if longer than that I would check with a doctor, but for now I would say you're fine, not pregnant, just need to relax a bit, you're going to be ok.