Diarrhea, joint/muscle pain, nausea, lightheaded, night sweats, etc.

Hi everyone. My husband has been sick for so long and we really need to figure it out. He is 42yrs old and before all this was healthy. It started out as what he describes as a very tense stomach, almost like an extreme nervous stomach feeling, around 10 yrs ago. Dr. Diagnosed him with anxiety and IBS and it was manageable for many years. (We dont think it was ever amxiety or ibs) Now in the last 2 years it has become debilitating. That feeling is there constantly 24/7. It wakes him through the night. He also gets pain in the uller left abdomen. He is not anxious at all but yet the feeling persists. Now also in the last 2 years a myriad of other symtoms have come up. Daily diahreah, joint pain, muscle pain, nausea, light headedness, bradycardia (low 40's), low diastolic blood pressure, drenching night sweast, 50 lb weight loss in 3 months , insomnia, syncope, brain fog, extreme fatigue. He was diagnosed with hypothyroidism and sibo over a year ago but even with treatment for both his symptoms are only getting worse. He has had scopes both ends, pill cam, endoscopic ultrasound, gastric emptying, echocardiogram, holter, cardiac stress test, mri of pancreas and surrounding organs, ct of abdomen pelvis and head, numerous ultrasounds and blood work and nothing come up that explain his symptoms. Only small things such and moderately elevated lipase for many years, a thyroid nodule, sinus inflamation on his head ct, high carotene he is orange, low B12, just slightly low hemoglobin, a slight enlarged spleen that is now normal sized, slightly enlarged liver, small kidney cyst on left kidney. We recently sent his blood to Germany to Armin Labs and yersinia and cmv came up but can that really last that long? His stool test was negative for yersinia as well so that is confusing. We are at a total loss. I know the sibo amd hypothyroidism can cause many of his symtpoms but I really feel there is a root cause to all of this. Any suggestions? We have near reached the end of what his gi specialist, endocrinologist, rheumatologist and cardioid can offer. Any ideas on the constant tight stomach as that is his most debilitating symptom. Thank you for your time.