Is bactrim causing my anal itching and irritation?

Patient: Hello, I am currently taking Bactrim 800mg for a UTI. I am on my 7th day out of 10 day prescription. With that being said, I have diarrhea daily once a day, its not constant. This is the 3rd day I experience anal itching or irritation, its moderate and uncomfortable and it doesn’t have pain. What should I do?