My dr 2 days ago run urine culture to check for bladder infection. No blood in urine. Dr sent me to ER to check for appenditicis. Ct scan normal, bloodwork normal, but had urine in blood 2 days later. Why does this happen? Do I actually have uti?

Agree with Dr Garber. If you are on, or just finished your period, urine will show blood. Blood means red cells, without white cells UTI (infection) is much less likely. Need to recheck urine to make sure blood is not still there. If still, with protein, need a nephrologist, if blood without protein in urine, need a urologist.
Consider False Pos. Urine can be tested for blood using a chemical strip dipped into the urine (dipstick) or by looking st the concentrated urine with s microscope, trying to find red blood cells. The dipstick may say there is blood when the microscopic exam shows no cells. Also, a few red blod cells from time to time may not mean anything important--you need to know how many cells how consistently.
? Kidney stones. I would like more info. Pregnant? Using medications? What is your diet like? Participate in physical activity? Sexually active?