Over the last year i have had mucus strings in urine. heavier in the morning and fewer as the day progresses. three naat urine tests show negative for gonorrhea and chlamidia. any ideas on what could be causing this?

I assume there is no mixture of your urine with bowel movements.I assume you have no symptoms of urinary burning,frequency,or urgency. Tiny amounts of mucus in urine is usually not significant but large amounts, especially with an odor, is different. A urinalysis with microscopic examination would give an idea of how much mucus is present&see if pus cells are present. ?Had culture ?Saw urologist.