I was urinating a lot and i was feeling dizzy. but it is mostly gone now. the only thing different is my left lower back now hurts. is it muscle problems or is something else?

Pain from muscle strain or arthritis usually eases with local massage or exacerbates with certain body position. Pain from internal organ such as urinary stone usually radiates to the groin/genital area along with the change in urine color, not improved with massage or body position. If pain persists or gets worse than yesterday, you should go to ER.