I realize you posted this quite awhile ago, but I was trying to find out info about endometriosis when I came across your post... I haven't posted on this part of healthboards before...
I went to my doctor for the pain under my ribs like you are describing!!!! He did a stool culture

and I had some type of bacteria and he gave me some antibotic to take and its gone!!!!!!!

Took the constipation and diahiria away too!! Hopefully this will help you if you haven't found anything out, good luck!
I go this thursday for an ultrasound to see if it shows anything. He seems to think I have endo, but wants to check for cysts, will endo show on the ultrasound??? Can't find that answer anywhere! Having terrible pains around right ovary area, swelling in my tummy, really heavy periods(irreagular), and I can't sleep for the pain. But it sounds as though if I had this my pain should be more present at cycle time, but mine is all the time. No relief!!!! And I have completely cut my Husband off (lol)

It just hurts way to bad!!!!
Good luck and thanks for any insight you give me!!!!
Lisa T