Constant UTI symptoms after period but NO infection?

After my period I always get UTI symptoms but I do not have an infection. The doctor has sent my urine to the lab and there’s nothing abnormal with it. But after every period I will have frequency, urgency, I itch, and have bladder pressure. I have to use pads (cannot use inserts like tampons or cups due to trauma) and I think maybe the chemicals in the pads are causing it. So I tried period underwear but it was the same. Or maybe it’s because I am constantly sweating in the pads/underwear. Eventually it does go away but it’s so annoying and painful and really affects my life. My period itself is not bad or heavy and I barely cramp. It’s afterwards that is so hard on me. Anyone have any idea what this is? The doctor basically just told me I don’t have an infection so there’s nothing she can do.