I am laughing because I do this a lot. I use the kind that works in your ear. I try one ear, and if that doesn't show me a fever then I try the other ear because I don't believe the first result. And when that one is negative, then I ask my wife where our other thermometer is because I don't believe it. Occasionally when this happens and I just know I have a fever, I will try again an hour later and I actually will have a fever. Now either it is mind over body and I'm giving myself a fever, or (I think more likely) I am just so sensitive to my body that I can tell a fever is coming on before I start to show a temperature. Other times I think I am just feeling under the weather; maybe a pressure system is making me feel crummy or I am having an inflammatory response to something I ate or maybe even just allergies. But occasionally, it turns out that I was right and the temperature just hadn't shown up yet.