why the HCTZ? this diuretic is given to people with problems controlling their diastolic pressure. Your diastolic pressure reading seems fine (low?) so unless you have congestive heart failure there would be little need for HCTZ (did/do you get swelling in the wrists or ankles?)
the OTC potassium is 100mg. Rx potassium starts at 8 mEQ and goes to 20 mEQ (750mg). a large banana is 6-8 mEQ. if you are losing potassium (you might be cramping also) through perspiration and your water pill then perhaps you are deficient. a CBC could easily confirm this. potsssium and calcium help to regulate your heart function.
there is a calcium and magnesium supplement (may also have zinc in it) that you should take along with some magnesium. i supplement with this all the time.
good luck.