another test kit, or take a smple to your lfs and have them test it
another thing, how do you clean your tester?? just rinse it, that is all, and (if you don't know this) never use your finger as a cap for the tester and never touch the dropper tip on the reagent bottle, your body oils can contaminate your equipment, enough to give you false readings, but if your alk is low, your ph shouldn't be high(shouldn't), so i would test both with another source, to make sure it isn't the testeer and to find out which one
what type of tester are you using???