Can endometriosis be in the spine?
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You might go back to your PCP and have the bladder thing checked out. You never know, you might have endometrial tissue in the bladder or endometrial tumors in the bladder causing the disfunction.
You might also consider googl'ing endometroisis to see if you can find out any other maybe supporting information to arm yourself with when you see a doctor.
I wished I had so words of wisdom for you. Just hang in there and keep complaining about your back, Lord knows I know you are in pain. I had bladder issues as well. Ended up being diagnosised with a bladder spasms. But there was no medication prescribed because I have epilepsy and the Dr. did not want to interfer with the meds. I was already on.
Take care of yourself!!!!