What do you suggest if I have an obsessive crush on my professor, am I crazy?

Psychotherapy. Can help you figure out what about the professor excites you more than his looks, etc so you can then know yourself better and find a good match for yourself.
Reprogram this. You're not going to have a romantic relationship with your teacher. This is asking for disaster and I think you recognize this. Decide instead how to reinterpret your feelings. "I feel this way because I want to be as learned / helpful / kind / effective as him." "I want to be a lifelong learner and to apply his lessons as I seek for love with someone suitable for me"