So my boyfriend and I had sex 2 days ago. We used a condom and he pulled out. Well while he was pulling out, I felt something drip and I couldn't tell if it was sperm or if it was sweat. I have had 2 shots. the first shot I had a period for like 2 months straight. The first one was in September. and the second one was on November 30th, I haven't had a period since the first one. how would I know if I was pregnant? what is the risk?