Strong heartbeat, 3 day growth

I went in for another ultrasound after spotting last week. The good news is the baby’s heart rate jumped from 94 to 130bpm. We were able to see the heart flutter and hear it.. it was magical!

However, last week baby measured 6 weeks 1 day and today 6 weeks 4 days.. my doc said everything looked good so far, but I can’t help but worry since I know baby should be doubling in size early on.

Doc mentioned that sometimes measurements can be wrong early on and also compared my first sono to the second and there is obvious growth.

Has anyone had this happen? What was your outcome? I don’t want to be too confident and have my heart broken next week when we do another ultrasound.

My niece was put back 2 weeks during her pregnancy during the beginning of her second trimester due to finding out late and everything is going great for her, but everyone is different.

Any feedback would be appreciated!