I'm bleeding when i pee and it burns & i only had sex once but used protection and then a few days later this started to happen.

Infection.: You may have a urinary tract infection (that is not due to a sexually transmitted disease). It's quite common in women. See a doc & get treated. Avoid harsh soap & fragrances in soaps, detergents & avoid fabric softeners. Too, avoid trauma (too much pressure) from thongs, tight clothing, cleaning too hard/roughly, & too much direct pressure with repeated intercourse in a short period.

Possible UTI: The blood in the urine, and the burning as frequently signs of a urinary tract infection. This is common after intercourse. You will need to see your health care provider, have a urine analysis done, and get treatment if this is a UTI. Do this today.