I'm a 69-year-old woman with recurring urinary tract infections. The latest shows ecoli in my urine. Why do I get these? How can I prevent them?

Urologist. Consider seeing a urologist for work up for frequent urinary tract infections. Office cystoscopic exam and vaginal exam are often performed. Many times low estrogen levels resulting in urethral lining atrophy is the culprit. Topical estrogen cream applied to the urethra often can make a big difference.
Urologist needed. If he found you normal and cranberry tablets did not help, try low dose antibiotic for a long time.