A lot of people here seem to be ignorning the fairly large percentage of sensais who are quite happilly married to former students.
In my head there is a sort of 'one strike' (or MAYBE 'two strike') rule. It's a bad idea, generally, to date inside the dojo (sensei or no sensei). However, it's a worse idea to pass up on twu luv. So, you get one chance (or at least I do). That's why the advice to take your time and really find out what your feeling seems like great advice to me. The advantage of your situation is that you know he isn't going anywhere and, in the meantime, neither are you.