PollyH, congratulations on becoming a grandmother!
It sounds as though you are like me i.e. you should really have a hysterectomy but struggle on in the hope of progesterone substitute.
I only became intolerant to synthetic progesterone and Utrogestan post menopause, I didn't have problems pre-menopause and had a Mirena coil for quite a few years but as soon as my own hormone levels dropped, my body decided to reject all forms of artificial progesterone including the Mirena coil which I eventually had removed.
It's a difficult one. If you can't tolerate artificial progesterone there is not much you can do about it other than severely limit its use. Will your gynaecologist allow you to simply stop using the gel every 6 weeks (for example) have a bleed (which should happen each time you stop the gel) and then start the gel again once the bleed stops? You would have to have regular scans but I did read about this method being used in very extreme cases while a hysterectomy is being considered.
I had a proper bleed one month after only taking just 1 x 100mg Utrogestan capsule vaginally. After just one capsule, I had a migraine and thought "sod this for a game of soldiers" and ditched out and I had a normal period 6 days later. Same has happened with 2,3,4,5 & 6 100mg capsules - yes, I've had to ditch out due to migraines many times but regular scans have shown a 2mm lining measurement. Obviously this will not be the same for everyone but it does show how some women can get away with less Utrogestan and if you are one of them, perhaps your gynaecologist will work with you and let you take the barest minimum? It has to be worth a try.