Are you bleeding? They way my doctor explained to me is it takes 2 weeks to conceive, and then another 2 weeks at least to show up. You probably didn't get pregnant until 2 weeks later than you lmp. Also, sometimes miscarriages can throw the cycle off as well. You said you lost the baby before, and I believe you know your body better than anyone. If you feel something isn't right, got to your OB. I believe as long as there is no heavy blood flow along with heavy painful cramping, you are probably ok. Not a doctor, but I am having my second child.