Doing it the "standard" way (at least the way we were taught in school) the pen rests between your thumb and index finger. In both cases, you "pinch" the end of the pen with thumb, index finger, and middle finger. But holding it the standard way, the length of the pen is largely unsupported (and so support has to be provided by "pinching" harder), whereas holding the pen between the middle and index finger provides passive support. From your question, did you always hold a pen between middle and index finger?