It is negligence. If you can get another doctor to say they would have done differently and tested for endo had you come to them and told them what you told that doctor, then you have a case. At least that's how it works if you're building a case against an EMT (learned from being in the EMT class in the negligence section).
It is consider neglience...however you have to prove it...its really hard to do, i tried showed that the doc actually did surgery and saw the spots and my overy was attached to my pelvic wall and without pics it didnt work well for me.