Hi Twig
Sorry to hear you are feeling low more frequently.
The problem with the Mirena is because it stops the periods you can't tell when you are reaching menopause so it could well be that you are post-menopausal or nearly so, and your oestrogen levels have dropped further.
However if you have fatigue then I would suggest you get a blood test - if not done so already, because low thyroid function can cause this and some women experience this around the time of menopause.
What is your diet like too? Some vitamin deficiencies lead to tiredness -, but this is unlikely if you eat mainly fresh food cooked from basic ingredients, plenty of fresh fruit and veg, fish, dairy, nuts, pulses, grains etc. Iron deficiency can lead to anaemia and tiredness.
Also testosterone declines with age and this can contribute to fatigue although this is not widely tested for nor recognised.
I presume you have the Mirena renewed every 4 years since starting added oestrogen as it is only licensed for endometrial protection as part of HRT for this length of time?
Maybe also you have developed sensitivity to the progestogen in the Mirena or maybe absorbing more into your system as time has gone by? Perhpas if you are now post-menopause or nearly so, then you could try a different progestogen - provided you don't encounter further bleeding problems.
I would make that appointment and have a good MOT - and if no other cause can be determined I would suggest perhaps think about increasing your patch to 100 mcg and see if that helps?
I hope these ideas are helpful and good luck!
Hurdity x