If you're having regular ultrasounds they would probably pick up adenomyosis. I have it and my uterus is large and heterogenous with diffuse adeno. Periods are a nightmare Panadeine forte helps a bit but I have to wipe myself out on them to have an effect Another thing I use is mersyndol. Have you tried it? It may help with the back pain.

I really hope you find out what it is soon. Take care x