Did anyones HCG stop doubling?

My hcg was was as follows:

October 1st- 721

October 3rd- 1728

October 5th- 4228

I then stopped having it drawn but ended up in emerge on October 17th at 6 weeks and 4 days pregnant with light spotting and an HCG of 73,000.

From October 5th at 4228 to October 17th at 73,000.. it would not be doubling anymore.. is this normal for it to slow down and take longer to rise? Baby had a heart rate of 142bpm and I had another ultrasound this week that I am waiting for the results.