I would start with a Metametrix GI Effects test and work from there. You really need to find out what the primary factors are first and start there. Self- diagnosis is an iffy path and seen too many failures. Some of these issues are quite complex and need some correct guidance.
Second thing I would do is look at heavy metal detox and mineral balances (which is overlooked sadly) Look at Traceelements.com for mineral testing. heavy metals should be either evaluated thru a heavy metal challenge (doctors data) or treat without lab results.
Any abnormal test results (blood)?
Vitamin D3 levels checked?
I would also look at homeopathy to treat viral conditions such as HHV6, cytomegleovirus, ebv etc.