I've had IBS-D since I was a teenager. Since this is a syndrome and not a disease there is no "cure" – you just have to find the foods that work for you.But, having said that, the food that is okay to eat yesterday, may aggravate the condition today. and, even though it is not a mental illness thing, your state of being is a very real trigger! So, I know that if I eat fried foods I will always have diarrhea. If I eat leafy green veggies, I will have diarrhea and really awful gas. Raw apples cause cramping. Ice cream, it's bad too but I love ice cream so I eat it at home. I guess because I've dealt with this for so long I've developed the ability to hold my bowels fairly well so I can't get to a restroom. My gastroenterologist recommended the FODMAP diet. Google it. It lists the foods that you should stay away from, the foods you can have in moderation and the foods that you can eat. But keep in mind, the food that you tolerated today, may not be okay tomorrow. You just have to pay attention to what you eat and how your body reacted to it and how severe that reaction was.
I still have IBS-D but have now been diagnosed with Lymphocytic Colitis. My gastroenteriologist has me on Budesonide 3mg 2 caps a day. Lymphocytic Colitis causes watery diarrhea multiple times a day(10-15) and is difficult to treat. The Budesonide is a synthetic steroid that does not metabolize in the liver so it is not as bad to take it for long periods of time. Bottom line, it has put me back to my new normal of 2-3 movements a day of soft to medium formed stools. I also tried Lialda but it didn't work as well as Budesonide. Talk to your doctor and see if he is willing to try either of these drugs.
Good luck. I know your frustration.