the ob/gyn dates your pregnancy based on the first day of your last period not when you had sex. if you question the date they gave you don't worry. you'll get an ultrasound that will tell you for sure. if this is because you are questioning paternity those dates are too close to be sure. you'll have to have tests done after the baby is born.
period feb. 2 and feb. 25. sex feb. 7 feb. 15 feb. 28 and march11 when did i become pregnant? always had irregular period. today is 4/11/15. never know when i ovulate.