What Is The Treatment For Diarrhoea Which Is Not Responding To Medication?

I was diagnosed with Diverticulosis several years ago. I have kept it under control with diet and seldom have a problem with it. However, last Sunday night, I started with diarreah and It is nearly a week and I still have it. I tried the BRAT diet but although I feel a little better, I still have it. I took my Gemfibrisol and Lisinopril yesterday and had gone off these for a few days. The pain is not as severe, however, I cannot get the diarreah stopped. I took an anti-diarreah over the counter drug yesterday and started feeling better. I didn't take it before going to bed and started with the diarreah again this morning. Please excuse the misspelling of medical terms. Oh yes, I do not have a fever or any other symtoms indicating influenza etc. At 4:00 yesterday, I tried to eat some real food and perhaps it was too early for that. Please advise. My age is 68 in case that is important.