Hi Liz
You are still peri aren't you? While 100 mg might be enough, the doses are an approximation and it is not possible to tailor them to suit individual women, and especially not in peri-menopause when your oestrogen and progesterone levels are fluctuating. If you are peri, then the chances are you will have cycles when you don't ovulate, in which case the extra progesterone will help to thin and shed the lining that builds up in between times.
I use 200 mg vaginally for a long cycle - as Stellajane says you can get away with less because more is absrobed, but the amount is guesswork and preferably carried out with the sanction of your doc to keep an eye on things.
re using it vaginally - yes "relations" are tricky eg when we've undulged I then wonder if I need to put another one in, in case it all the progesterone gets washed out so to speak! Side effects for vaginal use - it always irritates my bladder so have to get up in the night (I do anyway most nights but defo have to with utro). I also get thrushy type irritation between the upper labia but sort it out with Canseten or fungal foot powder if it starts, which always does the trick.
Other side effects - I get the dream thing too. Look if all you feel is tiredness and the dreams then that's brilliant - it is bound to have that effect (the tiredness) with most of us because it is a sedative and taken in high doses to ensure enough gets to the uterus. I tend to get foggy head after about 5 days which then continues for the rest of the cycle and sometimes get migraines too. Like Stellajane says though - it's definitely the best of the bunch in terms of progestogens!
Hurdity x
Edit - I mean "indulged" of course!