I didn't mean to imply that this is the only possibility but just wanted to point out that there might actually be a real physical reason for your pain that needs to be taken care of rather than just trying to control the pain with your mind & pain medication.
I am not familiar with all the possibilities & don't know that much about endometriosis, only what I heard from the lady I worked with who had suffered from it before I knew her. Your explanation of the pain just reminded me of what she had described. Just to ease your mind, she had a very healthy baby girl & went through the pregnancy with no problems so infertility is not an absolute outcome from it. She had it taken care of before she got pregnant once they determined what was causing her extreme pain & that it wasn't JUST PMS. Infertility I am sure depends on where it's located I am sure, & also how quickly it is taken care of. Of course, I am sure there are other possibilities that I haven't heard of or know about. That's why it's important to go to the Dr/Obgyn when we have extreme pain instead of just trying to control the pain ourselves. Yes, we do need to listen to our bodies. I know it's hard because we always fear that Dr's will think we are just overreacting to the pain. Even if there is nothing, its better to eliminate the possibility & free our minds.....or know there really is a problem & have it taken care of so that it doesn't cause worse problems as the years pass.
Just a few links you might like to read even though I am sure you can google yourself:
Mayo-clinic has very indepth information (along the left side are many selections you can chose to find more (symptoms, causes, risk factors, complications, preparing for an appointment, tests & dx, treatments & drugs, etc):
http://www.mayoclinic.com/health/endometriosis/DS00289
What it is:
http://www.endometriosisassn.org/endo.html
Related with the environment & toxins:
http://www.endometriosisassn.org/environment.html
Definitely don't worry about it until you know exactly what is causing your pain, but it's important to be educated & either have the pain dx'ed or have dx's eliminated to ease your any worry. Usually when there is extreme pain, there is a reason & a Dr needs to be addressed. It may be necessary to use pain relief techniques after you find out what is causing the pain, but knowing the cause is the first step coping with the pain.
Best wishes,
Debbie