UTIs every time I have sex

I was just wondering if anyone could help me please. Everytime without fail I get a UTI after sex. I pee after sex, im clean, no STI’s etc. I do everything that your meant to do. It doesn’t matter who I have sex with I have always ended up getting a UTI. And it’s really draining and I don’t know what to do anymore. Im worried im going to get resistant to the antibiotics eventually and be stuck with one forever :(. It really affects any relationships I have because I’m reluctant to have sex after Iv got better again because I don’t want to get a UTI and hate life again

Does anyone know a solution to this? Iv had bladder scans and they all came back normal, my pee bizarrely also comes back normal unless they test it straight away, I’m guessing the germs must die on the way to the lab and not be traceable? I don’t know