My original due date was 12/10 and has changed to 12/21. It is very concerning to me and I'm so ready for my ultrasound next week. Blessings to each of you.

Happened with me! My due date was December 5th and based off of my last period but I knew it was impossible because when it was saying I conceived was two days into my last period lol. Plus I did ovulation strips and knew exactly when I ovulated and made me earlier. It all depends when you ovulated! Now my due date is December 16th and the baby had a perfect strong heart beat. I'd only be worried if it was a few weeks early like it was with my first one which resulted in a miscarriage.

I was due 12/3 and it was changed to 12/12. I'm a tad nervous and go back next week for a follow up US but I'm hoping everything is okay 

Happens all the time. My original due date was 3/15 with my last pregnancy and it was changed to 3/18. She was born 3/20. Babies grow at different rates, and the due date is just an estimate anyway.