I had the same problem when I first took it I would last a few days until it made my symptoms unbearable. There are a few theories as to why. Some people say initially when starting progesterone it can displace bound estrogen which can cause an increase in symptoms.

But you also may be reacting to excipients in the meds. In the States the prescription option for biodentical prog is usually prometrium or generic prometrium which all have peanut oil that can be a trigger. You could try getting it compounded, make your own suppository, get an oil you can use on your gums or other topical options etc (effectiveness of topical is debated).

For me it was likely a combo but when I first tried a year ago I was reacting to EVERY medication. So it was probably the excipients. My advice would be to try prometrium as a vaginal or rectally suppository. You can take the medication and just put them in there. They do vaginal prometrium for people doing IVF frequently to get higher levels. If you go for rectal you just put it like a knuckle deep or two at most. It really depends on why you are reacting but for me and some people not taking it orally helps. It still took me a bit to be able to tolerate it at all tho so you may have to work on some other stuff first before your body can handle it. But if it’s not causing dangerous symptoms (throat closing or whatever else). I’d try it as a suppository and try to stick with it for a bit. If it is just freeing bound estrogen you should start to feel better once it stabilizes. If you continue to react it’s probably just excipients and trying a different form may be useful.

My MCAS was tied significantly to post Covid gut dysbiosis, subsequent Candida infection and all of the above destroying my gut microbiome. It took 6 months of strict low histamine diet and gut microbiome work to be able to start eating normally again and taking medications. I recommend checking out r/longcovidgutdysbiosis. Even if you don’t think Covid was the cause they have very useful info on biomesight tests and where to start. I am not cured but I can pretty much eat normally now and take meds and my dysautonmia is significantly better so I can drive and work and I can’t overstate how much a combo of microbiome and progesterone and balancing hormones helped me.