Could be 'referred pain'. I'm not a doctor, but sometimes issues in one area of the body can cause pain in a different area. Pressure in the abdomen causes pressure on the diaphragm causing pressure in the chest area...see?
Your headaches could just be from the stress of not knowing yet.
It seems you're doing the right thing and tracking down the true 'culprit'. Hopefully you will have your answer soon.
multiple surgeries for rotator cuff both shoulders with residual chronic impingement syndrome, ulnar nerve transposition, carpal tunnel release, multiple wrist surgeries, multiple herniated discs, tarlov cysts, whiplash, bursitis of hips, grade 5 right shoulder separation and torn labrum, ovarian cysts, fibroid tumors of the uterus