I had horrendous kidney pain (at least I think it was my kidneys) years ago and had every test under the sun (ct, X-rays, cystoscopy, IVP, urinalysis etc.). All they found was a cyst in my left kidney that had possibly bleed into itself. That torture went on for the guts of 8 months. I was bed bound and in agonising pain, begging the hospital to remove my left kidney. They didn't but sent me home limping and with painkillers each time.
4 years later (after years of what I thought was bad IBS) I woke up one night in agonising pain.. Passing out, vomiting, you name it. I live alone in London so I couldn't get myself to hospital. After 6 hours it subsided enough that I could get to the walk in clinic where the doctor said she thought I had an ovarian cyst rupture and possible endo. I was able to have lap, hysteroscopy and cystoscopy three weeks later (privately) and was diagnosed with quite sever endo on ovaries and a few other places plus adhesions etc.
The path to diagnosis is a tough and lonely one. I hope you get the answers you so desperately need and meet compassionate doctors along the way. And don't read all the horror stories: Your kidney issues may be totally unrelated to endo and it could be a kidney stone or indeed an infection that's gone undetected.
Take care of yourself and keep me posted. I know how unsettling it is living day by day with the worry of pain and your health.