What is digestive tract ulcers (rare) other than Crohn's or TB or other infectious diseases that many GI specialists not undiagnosed after all tests?

Keep at it. If multiple GI specialists are stumped after having the results of endoscopies and pathology reports it is not likely that guessing over the internet is going to solve this problem.
I.B.S. Monitor blood levels for tnf and aso antibodies also. But there are test to differentiate ibs from chron's disease.