Did your dr tell you when to use Utrogestan?
It seems slightly weird the way you're timing it (sorry!)
Normally, there are 2 ways:
1 On the first day of each calendar month (so it sets a cycle.)
2 In the middle of a cycle (ie the latter half as would happen with a natural fertile cycle.) That's why is says day 15 x 12 days.
Your timing doesn't fit with either. If you own cycles are very short, then midway would be around day 12 (half way of a 24 day cycle.)
The aim of Utrogestan is to thin the lining/ stop it overgrowing with the added estrogen.
If you are taking it while you are bleeding with your own period, it's not really working in an HRT 'cycle'.
If you still have regular cycles you should take it in the middle- so roughly 12 days after the first day of your period.
If you are not having a period each month, you can try to re-set your cycles by choosing any day of the month and always starting the utro on that day. ie - the 1st, the 10th...etc.
As you are in peri you might get your own light period as well as the withdrawal bleed, occasionally.
Really, all this should have been explained by your dr! What are you paying for if they aren't communicating?
The reason I split my dose is a) I find it dries easily b) initially when I increased to 2 pumps from 1, I did feel slightly nauseous. This was very early days- I've been using it now for 11 years.
However, when I increased to 3 pumps (this was ages ago and only for a while) I didn't feel nauseous at all.