People think that "fruits and vegetables" are healthy, but some of them may not agree with you.
Vegetables and whole grains can be very good, but some people do not tolerate soluble fiber (barley, oats, beans) and others do not tolerate insoluble fiber (whole grains, fruit skins).
Here's a chart with more foods:
List of Foods High/Low in Fiber; Types, Health Benefits
If you tolerated gluten before, I'm sure you can it now. I'm not aware of any side effect of gluten in people who do not have celiac disease.
If you tolerated milk and all dairy before, you can probably tolerate it now.
Make more experiments and eliminate foods one by one or try a "low-FODMAP" diet, for example. This eliminates soluble fiber, fructose, lactose and polyols.