I was 23 when I had a hysterectomy. Severe endo. It was on my bowels, bladder, spleen, spine and gallbladder (which had to be removed). A friggin mess.
My 26 year old DD has Stage 4 endo - diagnosed at 17. She's had several "clean-up" surgeries, lost an ovary at age 22 (endometrioma cyst). She conceived my 2-year-old GD via IVF (she also has an angel baby conceived via IVF).
Anyway, 26 yo DD was recently diagnosed with hypertension! This does not run in my family (early onset hypertension). She also has had IBS since she was 17 (we do know that is from the endo on her bowels). Anyway, turns out that the endo has gotten so severe that it's on her liver, thereby inhibiting it from functioning properly (her cholesterol levels are through the roof and she has a great diet), coupled with poor blood flow because of all of the endo everywhere else in her body. She even has endo on her bladder and suffers from cystitis and blood in her urine. She's going to try one more round of IVF after one more clean-up surgery, then the ute is coming out (and most likely the other ovary). Personally, I wish she'd have the hysterectomy now, but she wants to try for one more baby.
Endo can affect every organ in your body - including your heart and brain (from blood flow issues). It is very important that you see a GYN who specializes in endometriosis. Endo cannot be detected via sonography - only through laproscopic surgery.
It was good that you had the GI workup - no matter what the cause of the issue, it should be treated accordingly (PPIs, IBS meds, etc.)
Please KUP - will be praying for you. I sympathize - endo sucks.