pmz, write what you hear in your head, and call it whatever you want.
Your original post begs the question, have you studied your basics in music theory and composition. My guess is the answer is no, so rather than aim right away for a fugue, you would probably benefit from doing a lot of figured bass and harmonization exercises, and learn the old rules of counterpoint (the species of counterpoint), then learn some canon technique, then do a few two-part fugues.
Or, find Glen Gould's recipe. Very funny.

But really, all that is for naught if you have something in your head that is obstructed by technical knowledge. Knowing more may inspire you and free you, but you should not let rules get in the way of your creative spirit.