I Have Had Chronic Diarrhea For Years Now. I Am

I have had chronic diarrhea for years now. I am 58 yrs. old I've tried everything lactose meds, fiber supplements , probiotics , had a colonoscopy. It seems everything I eat goes right through me and I'm constantly in the bathroom. Lately bm' s have been very watery and black. No pain involved just gas and need to get to a bathroom instantly. I have even had accidents including during the night. I am on meds for major depression, cymbalta, lamictal, kolonipin for anxiety, take levothyroxin for hypothyroid and Crestor. What could be wrong? My physical doesn't think there is anything wrong. What is your opinion? Thank you