Uti culture came back negative. why is my urine cloudy?

False negative urine cultures are unusual & I assume that you didn't take antibiotics before the test. Various non pathological types of sediment in urine can make it cloudy. I assume you have no obvious symptoms of a UTI like burning,frequency,urgency,voiding in small amounts and nocturia. If you do, repeat the culture.

Try drinking plenty of water and emptying bladder frequently. If still cloudy you need to be checked by a Urologist. Hope you do well.