People vary a LOT in the types and amounts of bacteria they carry in and on themselves. You may naturally have a higher e. Coli count than the "average" person, and in this case, it may be lowering the threshold to trigger a UTI. There's not really any tried and true methods to alter something like that (if that's the case). E. Coli doesn't necessarily have to travel directly from your anus either, it can be on your skin or even live at a non-symptomatic level in your urethra already.

I had chronic utis too and taking a preventative antibiotic made my life so much more bearable. This is usually a single, low dose and basically just knocks back the colony count a little before it can cause an infection. I know many people (rightfully) can be wary about taking antibiotics this way, but it did give me lots of peace of mind and prevented me from taking frequent, full rounds of Cipro multiple times a month sometimes.