I am going to share my story and it will hopefully give you some hope:
1st US: 7 weeks according to LMP-baby measured 5w6d couldn't detect heartbeat
2nd US 2 weeks later: baby measured at 6w 5d with strong heartbeat (only grew 6 days worth in 2 weeks!!)
3rd US 6 days later: baby measured at 7w4d with 140 bpm (grew correct amount)
4th US: baby should've been 9w5d based on last measurements, measured at 10w4d!!
It appears our bean is catching up, and my doctor has now officially admitted that she might not have gotten accurate measurements in the early stages as being off by 1mm can mean a whole week off!!!
Good luck and I hope this gives you some hope! And stay off of google!!!!!