Maybe not what you're looking for as far as pain killing, but I get major relief from taking dandelion root tea. It seems to be really anti-inflammatory for my body as well as a diuretic, relieving pressure in abdomen.
If you believe you have more nerve pain than inflammatory pain, I don't know of an OTC that works on nerve pain. NSAIDS each have their own side affects on your GI system if you have to take them regularly, so you might alternate them since the endo and GI are probably sharing space and resources. And if one like naproxen loses its potency on you switch to IB then switch back. I personally prefer aspirin for systemic discomfort, IB for front cramps, NS for legs and back pain but NEVER take nsaids together or on same day. Tylenol is not an NSAID so u can combine that with an NSAID. Do not take tylenol more than A pharmacist will know a lot more about analgesics than a doctor, so find one and pick their brain about pain.
Try taking a combo of lots of B vitamins for nerves. Also I do yoga-like stretching, take hot salt baths, you know, whatever I can to get some relief. I usually can't digest food, so I make healthy smoothies or juices to stay alive lol. It takes a lot of energy to digest food, so you can help yourself out by doing that.
I do remember trying to tell my mom about the pain and I think she literally waved it off. I remember writhing on the floor with arms around my stomach and my dad yelling at me to get up. I empathize with you. I can't take hormone BC, I have some kind of hernia left over from a botched IUD, I'm allergic to latex, I have elevated testosterone for a woman I guess, but every time I get to a doctor I come away literally with more health problems or no progress at all.
Doctors really can only offer the standard best practice they are trained to respond with to the pieces of data about you that they choose to consider important. You're going to have to take a "wholistic" approach because only you know your body this well. There is never going to be a one pill solution. My cycle affects all of my organ systems, and keeping that in mind, I can manage it from more angles than a typical specialist usually will.
Don't use the words "nutrition, supplement, integrative, vitamins, etc." With your doctor, because she might just make you feel silly, and none of those words should be blindly excluded from health care. Just keep trusting your intuition and keep trying.
Dandelion root tea!