Bleeding .

Has anyone ever had blood in their urine and it be nothing ? I went to E.R. yesterday and everything is fine with me and my baby girl . They couldnt figure out why i had blood in my urin . I do not have a urinary tract infection. Or bladder infection or a kidney stone /infection. They were stumbled as am i . They checked me and my cervix is closed tight .ultrasound came out fine . I am baffled. Oh by the way im 23 weeks .