If regular meds have not helped your dog, and the diarrhea has been going on for a while, you might seek the help of a specialist. They might do specialized tests to rule out more serious issues like IBD (inflammatory bowel disease). They might do a colonoscopy and specialized imaging to look for other issues. Then they can prescribe a special diet and medications specifically for the problem. We did this with one of our dogs once that had constant loose stools. That way you know exactly what is causing the constant diarrhea. Hope this helps you.