most of the books describe some of the things that affect the readings. First off, get rid of the alcohol. It dries the skin, and research shows that it doesn't prevent infections and better than good general hygeine (that is washing your hands) unless you rub the alcohol, WITH FRICTION, for at least one minute. (thats what they do when I give blood, and its really irritating to the skin, but they are sticking a great big needle directly into my vein, so I put up with it then).
So a good soap and water wash a bit before your poke for bs. Dry well. do NOT squeeze the finger. some people wipe away the first little drop and test the second. I have done both, and found no difference in readings. So now I don't bother. I would chart both readings for now, and continue charting and see if its just a fluke.
remember too that within the allowable error range can be quite a range.
zen and the art of weight loss, finding the true path of en-lighten-ment