Muscle Weakness, Heart Rate 140, Bp 156/98, Low Potassium, Rbc In Urine, Fast Heartbeat. Potassium Supplements Prescribed. Suggestions?

I have had muscle weakness throughout my body and pins and needles feeling in extremities for over a week. Mostly on one side, but just recently on the other side also. Ended up in the ER feeling dizzy and very sick the other night. Heart rate was 140 and blood pressure 156/98. ECG was fine, just the really fast heart beat. Blood work showed low potassium. Urine analysis showed red blood cells in urine. I was given meds to lower blood pressure and slow heart and given potassium. I was sent home with potassium supplements and told to follow up with my pc. Will get into see him in two weeks. What could possibly be going on? I am a 53yr old female, 5' 3', 120lbs, very healthy. My normal bp is 98/64 and pulse around 64 to 68. No previous medical problems. I exercise every day. I eat very healthy and take supplements and vitamins. Why would my potassium be low and why blood in my urine? Can this happen for no reason or is there something else going on that will need to be treated?