Hello
Notheristerine is given in addition to the Mirena coil to stop bleeding. It's given in larger doses for bleeding than it is for HRT. As others have said it can cause PMT, it did for me. I was prescribed it alongside the Mirena too.
Now you have stopped taking it, I think you are experiencing progesterone withdrawal. If you put it in the search bar on forum, there's quite a few of us who suffer with it. Weepiness, low mood, etc.
It will get better as days pass.
I had same problems as you and ended up having a total hysterectomy.