Deetle, I don't know if you ever answered the question about how your periods have been before hrt. Were you without periods for at least a year? Were they still regular? Problematic? It is standard to take progesterone cyclically unless you are postmenopausal, without periods for at least a year. Or after taking it cyclically for a year, you would then switch to taking it continually. There are some here that take it continually or near continually while still in perimenopause, but that is not how it's normally prescribed.
There are lots of threads on here that mention the mood plummet after finishing a course of progesterone. It's common.
Take what I say here with a grain of salt, because I'm still not completely balanced. I also feel better on the progesterone, and I did not get a noticeable withdrawal immediately after the progesterone, but my panic is worse during all of my estrogen only days. By all that I've read, that would indicate too much estrogen, but actually when I increased the estrogen the panic hasn't been as bad. I take progesterone 10 of every 28 days. Since increasing the estrogen, my anxiety didn't ramp up until 5 days before time to begin progesterone again. It's possible that you still need more estrogen. This is where you just have to take a guess, give your hrt regimen a fair chance to do its work, then make changes if necessary. If the increased estrogen doesn't continue to improve my wellness, I'll be asking for continuous progesterone before my one year mark too.