UTI symptoms but negative urine culture?

I had sex with my boyfriend a few days ago, and since then, I’ve been having some UTI symptoms.

Frequent urge to urinate, uncomfortable feeling at the end of my urine stream, etc.

I do not have any burning sensations.

Went to the doctor and was prescribed antibiotics, but my urine culture came back negative. There is no infection.

What could this be? Do you think I irritated my urethra while we had sex? How long do you think it will take to go away?

It is not an STD. We are each other’s only partners and we have both been tested with negative results.