Well i'd say that you should give it time, dont get too exited about your fealings just relax and let them take their course.
you could simply have a crush on your sensei, the best way to find out is if you bide your time, when the dojo 'Family' go out go out with them, dont miss it just because he's there you need to be confortable and relaxed and your true feelings will show. If say in a few more months time you talk alot and get on really well and the fealings are stronger then ever then i'd be tempted to go against what ppl have said here and say go for it, ask him out! if you deny your heart even the heartbreaks then why are we here? even if he is your teacher that shouldnt stop you NOTHING should stand in the way of the heart it is what drives us to carry on and learn (of course all the motor functions are controlled by the brain etc...but you know what i mean)
BE YOURSELF (seriously stressed)
and see how you feel a few months from now
hope it works out.