Well the obvious place to start with diet elimination is dairy and gluten. I see you drink kefir.
Try giving up all dairy (kefir, cheese, milk, yogurt, etc) for a week and see if your symptoms are the same or less.
Then you can proceed to the gluten.
Those are the biggest offenders but there are others: fructose(that can be in your probiotic as FOS), caffeine, yeast (like in beer or other stuff), the list can be long but start with the first two.
When I switched to non-caffeine tea I found that was worse than green tea (weak) for me. The natural stuff in chamomile or similar tea drives my colon wild. Go figure. It should be really good and healthy, maybe for others but not my colon.
In remission April 2010 after 10 years of suffering and no remission ever
Jan 2010 started SCD diet (modified to remove dairy, fruit & juices)
Gluten-free=bleeding stopped in 3 days, 95% remission in 5.5 months on SCD
at 5.5 month stage homemade yogurt, hard cheese and some fruit OK
SCD Diet: Gluten/grain-free, starch-free, low carb, low-sugar
Supplements: tsp. fish oil, Vit D3 5000 with oil/fat, veggie juice, sunflower seeds, VSL#3, (4) Citrucel, (1) turmeric capsule, (1) calcium
Highly recommend: the book "Life without Bread" and the Specific Carbohydrate Diet
Rx: (6) balsalazide daily, mesalamine enema occasionally