Thought I had a miscarriage, ultrasound showed that I didn’t, please advise?

Hello – I am currently 5 weeks 4 days pregnant. Over the weekend I had a scare, and thought I had a miscarriage. However, the ultrasound showed that I didn’t. I did a beta three days ago, and my result was 17,243 and today I did a beta and the result is 31,988 with a doubling time of 78 hours. At this stage of the pregnancy, I read that beta numbers slow down. My beta numbers were doubling very fast last week and until 5 weeks 1 day. Are my current numbers (doubling at a rate of 78 hours) ok for week five? Or does it have to be exactly every 48-72 hours? thank you.

Age: 34
Female
Medications: progesterone