Four months seems a very long time to be bleeding.
My mother in law (this is going back 27 years) had 8 weeks off bleeding, they gave her hysterectomy.
I myself coming up to two years ago had a hysterectomy for heavy painful periods, ovarian cyst and endometriosis. I wanted to go the Mirena direction, but the gynaecologist recommended hysterectomy because my uterus was double the size and they found after the operation 7 times the weight it should be.
You could always get a second opinion, which I imagine it's not a easy thing to do in the UK at the moment. I'm from Australia, so it's not a problem seeing my doctor.
I hope all goes well and the bleeding stops