Im 10 weeks and I still have the stretchy like pains you talk about. My doctor told me that's a good thing. It means the baby is growing healthy. I myself had a miscarriage around this time last year && im very scared. I can't make an appointment just yet because of my health insurance. Im anxious to make one. I just want to know everything is okay. As for the due date, they measure the fetus from side to side and up and down. The fetus probably moved during the mesurement. I wouldn't worry to much about that. Just have faith && make sure you eat healthy && do everything right :) that's what im doing lol.
Hello and congrats on your baby! As for the due date being your first child you can either go 2 weeks early or 2 weeks late. Its kinda hard to tell right now exacty when you will be due cause its usually a guess. The take the length of the baby crown to rump, baby's head size and try to determine exactly how far along you are. However, babies can grow at different rates. So it may change again before you deliver. To be on the safe side use the newest due date they give you and try to make sure you have everything done a month in advance. That way if you deliver early you will be ready. As for stretching pains that is pretty normal due to the fact that your stomach muscles are stretching to make room for your uterus to grow and make room for the baby. As long as you are not bleeding you should be alright. Don't change position suddenly and roll out of bed instead of sitting up. If it gets too uncomfortable you can get a belly belt for support. I hope this helps you. Have a happy healthy pregnancy and delivery.