Men and women can’t be friends. And since he’s no longer your professor (I believe you said he taught you for a year, and your’e no longer in his class), the relationship has changed and you’re having trouble defining it. You’re not dating. You’re not professor/student. You’re something else — and you’re having trouble with what it is.
My advice is to be clear with yourself first. If you want to date him, then you have to act like you want to date him — and not as if you’re still his protege or his friend. This will be a little tough for you because you can’t treat him like a friend any more, and you’re going to have to be the one to make the changes. If you need to, you can tell him that you don’t want to be his friend because that’s not working for you any more. But more importantly, be clear in your own head and in your behavior.
I hope that helps. Let me know if you have any other questions.