Utrogestan with irregular periods

[OhTheSilence]

I've been on HRT for 4 months but still not sure when to take it, as my last two periods came after 6 weeks, then 2 weeks.
I had taken Utrogestan (2 pills) on the same calendar day each month (eg the 5th of each month), but that meant that the last time I took it, I was having my period.
Instead of the calendar days should I be counting 15 days from each period, regardless of the length of the cycle?

I should add I've been taking it for the 12 days per month

You are right to take it on the same day each month.

You are fairly new into this - 4 months- and it may take a while for it to settle and to override your own cycle.

Instead of the calendar days should I be counting 15 days from each period, regardless of the length of the cycle?

No because as your periods get further apart that just won't work.

Thank you!