If you even consider that you are (as you say, you can't decide), then you are not. People who are insane think that they are NOT insane. THAT is one of the characteristic signatures - quite like an alcoholic!
Fortunately, Surface Pro scientists have already devised a test to answer this basic question. There is only one question on their test and here it is:
Does the stylus' on-screen pointer bother/distract/obstruct you?