question: Hi doctor, I am 18 weeks 2 days pregnant. My friend told me that I am supposed to add two weeks to those 18 weeks while counting. Is that true? Can I get pregnant if I had sex during period? My period was on the 28th and I had sex on the 5th. That time, my period was on, but not heavy. Could I have gotten pregnant that time? How long do sperm stay in the body? Please explain.