Progesterone drop on PIO

Rachael • Married to my wonderful wife, mom to D, twins on the way. lots of other roles and titles.
Have any of you had a 2 point progesterone drop while taking PIO shots. Last week I was at 20.9 and this week 18.9. The doctor says this is normal but I'm freaking out and also worried because my symptoms aren't as bad as they were. I spotted earlier this week...not badly, they did an ultrasound and everything looked fine.