I presume youve already seen a gynaecologist as you know the size of your fibroid. Did he/she talk about surgery?
I had dreadful periods, just like the ones you're describing. Tranexamic Acid and the Mirena didnt help at all, in fact the Mirena made it worse. It turned out I had several fibroids, but the one causing the problem was in my uterine cavity, the others were in the wall of the uterus.
I had the problem fibroid removed. I was warned that if they couldn't get it out then the only other solution would be a hysterectomy. However, the op was a success and it's much better now.
As I understand it, there are different surgical options depending on where the fibroid is. Endometrial ablation wasnt an option for me.
I think you need to go back to your gynae, and explain that the solutions offered do far have nor been effective and that this is seriously impinging on your life. My gp was very reluctant to refer me, until I took in a diary of my period with entries on Day 10 (!!) about needing to change all my protection every 20 minutes.
Do insist on further investigation/ action. Good luck!