True, healthcare for women's issues is quite horrible (I have severe migraines and if more men were affected, there would be better treatments).
But endometriosis is difficult to diagnose without invasive procedures. If you are "lucky" they can see an endometrioma on an ultrasound.
What they could do more, is assume from the symptoms that it may be endometriosis and prescribe hormonal treatment for it, and see whether the symptoms improve.