White flakes in urine

Okay, I’m 7dpo today and I have had lower abdomen cramps for the last 2 days but super mild!!!! I am someone who has to pee frequently anyways since I thought this may be a UTI. I did take a UTI test with an over the counter kit and it was shown to be negative. I pee frequently including like twice at night time too. I have never seen the flakey white stuff in my urine before. Does anyone have any idea what it might be? Just wondering if it could be pregnancy related....we are trying to conceive !