Thanks Dangermouse.
Certainly sounds like what happened to me. I've read recently that prolactin is a better measure of real E level as it goes up when E is high (often in tissues and not measurable). My prolactin is high.
Noone in the UK believes prog can trigger this estrogen release, including my private bhrt clinic!!! But it's a well known phenomenon in the US.
I did work out, after 12 months of trying, that my dose is 25mg compounded cream. But, to be honest, I think I'm better on nothing than the cream right now.
I think it's something I should keep ready to use when my own E buggers off. In fact, I think some woman use it post meno so they can actually release that extra estrogen.
So, for the time being, I'm trying agnus castus.
That said, I've spoken to scampi and I think she should give the prog cream a try. Plenty don't seem to have the experience you and I had Dangermouse. It's all trial unfortunately.
I think, to add to your theory - I was taking bio clear estro for 6 weeks, which tanked my estrogen. I felt better, but it also gave me severe gastritis (that I'm still battling now). So I know it's all my E/P balance.
I've learnt a lot in the last 12 months - mostly how little we know in the UK

Scampi - I am wondering if your prog level is so low because of the mirena?! The progestin is meant to replace your progesterone, but progestin won't show in bloods... I don't think.
Anyway, there was a lady on our previous thread who took progesterone cream alongside the mini pill I think. She found it worked. Definitely worth a try for you.
Xx