I Have Trouble With Low Potassium. My Last Blood Check

I have trouble with low potassium. My last blood check showed the potassium was 3.0, and that is after taking prescription 20 MEQ potassium pills three times daily. I try to eat oranges, potatoes, and I drink a lot of 100% tomato juice. I am still having a lot of cramping in my hands and lower legs, and am physically drained. I don't know what to do. Should I go get my blood tested again? It was just checked on Friday, but I feel so miserable.