Hi, sounds great Harry, if I could just add a little to your fiber advice...
Broadwaynight, Harry is right, the fiber could be your lifesaver, but fiber spikes could cause you problems that you can mistake for food intolerances. You should count your fiber intake, first week 5 grams per day, increase 5 grams per day each week, so the second week would be 10 grams, third week 15, fourth 20, etc.
When I did this, at the first of each week, I would have symptoms, but not as bad as before I had started. Toward the end of the week as my body was tolerating the increase, I would feel great, it is a bit of a nuisance building up to the 20 - 30 grams, but it is very worthwhile.
The yogurt is wonderful, but it may be an idea to change one thing at a time, I would suggest you get your fiber levels up to 20 or 30 grams before starting the yogurt.. & when you do, you probably know from reading in this forum, the yogurt should contain active cultures.
If you don't know what fiber foods contain, there is an article in here [by me

] that lists fiber content. If there is a food that is not listed, just search on the web for fiber & dietitian, should be able to find it.
When you had all the tests, was gluten allergy one? If not, I would strongly suggest you have one, so you know if you can tolerate wheat products.
I hope this is helpful, the fiber control has certainly helped me. There is very little that I cannot tolerate now.
Good luck with whatever you decide to try.