UTI’s after sex

So my parents don’t know i am sexually active... I’m 20 and a junior in college... but every single time i have sex i get a UTI... i pee right after and drink tons of water... my doctors don’t know i am sexually active because my mom comes with me to all my doctors appointments... please help.. idk what to doo

UPDATE: since my mom has always gone with me and i live at home she would know something is up if i ask her not to come.. and my mom’s friend is my OBGYN (i know all the legal issues but I’m still scared) also every time I have the symptoms of a UTI i got get an antibiotic.. I’ve only been with one person who has been check for STI’s and is negative