HCG falling for 3 weeks, now rising?

I was/am having a chemical pregnancy. My HCG dropped from 70 to 61 on 11/24. I have had weekly draws sense. It went from 61 to 52. Then 52 to 23. Now this week it went up to 40. I had a 48 hour draw after that and it was 47. I have another draw Monday. Has anyone experienced anything similar? I have had an ultrasound that showed everything looked clear last Wednesday. Could retained tissue just now cause a new rise 3 weeks later? I am lost and honestly it seems like my doctor is too….