If it were me, what I'd do is stop using the Ketostix! Hate the darn things. Quite a few things can affect the readings - the more water you drink (which is good) the less of a reading you will get - that is why dark is not necessarily good - oftentimes it means you aren't getting enough water.

You may very well be doing nothing incorrectly. Some people never/rarely show a trace on those things - but still lose weight. Some people sear by the little sticks, and it makes them good to see "proof" - but IMHO, that proof is too subjective.