I've been taking an antibiotic for a uti. now my menstruation is late. this is my first uti in my life?

Pregnancy test: The first step after a late menstrual cycle is to rule out pregnancy. Take a home test to make sure. If negative then give it some time. A One time late cycle usually corrects it self eventually. If you continue to be irregular over the next few months then see an obgyn for options for cycle regulation

Speak to your Gyn MD: You may have low levels of estrogen , it is responsible to maintain healthiness of vaginal mucosa , lack of it will lead to bladder infections , altered periods . Let your gynecologist evaluate you and set a treatment plan.