I had blood in my urine (everything else wad fine) but my urine culture came back normal. What would cause me to have blood in my urine? I've also had left flank, back pain and lower abdominal pain.

Multiple causes. Kidney infection, kidney stones, old menstrual blood mixed with urine, sexual trauma, urethritis, etc. If this continues recheck the urine; however, I suggest a helical CT scan of the kidneys to look for a stone as well as a pelvic ultrasound. Please seek medical attention. ASAP.