I'm glad that you're so aware of the unhealthy nature of this obsession -- being in denial in this situation could exscalate it into actions that would be very detrimental to the privacy of your teacher, or something related. So first off, good job being honest with yourself!

Do you see a therapist/counselor for any mental concerns right now? Do you have other obsessions, or engage in compulsive behaviors? Even if the latter isn't applicable to you, getting some counseling or therapy for this problem may be the only way to really get over it and move on.

You might want to start by asking yourself why a gorgeous teacher would affect you so strongly. Why do you think you responded like you did, while other guys in the class might have just attained a mild infatuation.

Often such an obsession arises when you feel like having such feelings (and possibly sexual thoughts) about an authority figure is wrong and unacceptable. So everytime the thought/feeling comes up, you panic and try to supress it -- but the more you try, the worse it gets. If this is the case for you, it would explain why other boys could let the thought pass by, because they didn't feel guilt over having it, or could come to accept the guilt instead of feeling desperate to smother the thoughts to make it stop.

This may or may not apply to you, or it could possibly apply to you without you being very conscious of it. A cognitive-behavioral therapist would say that the feelings of guilt spring from "automatic thoughts," beliefs that are so deeply ingrained that you often are not aware of them unless you probe for them.

Anyhow, even if you feel like this isn't a big enough problem to seek professional help for, many people go to therapists for mild to moderate hang-ups they have -- wisely recognizing that they need better resources to tackle a problem that they are stuck on.

You can see how continuing to try to solve your problem with your current coping mechanisms would be a futile attempt. And you also see how it's impairing your real relationship, and how that's not fair to the girl (or yourself). Please don't let this drag on, you might miss out on a great (and healthy) relationship.

Jessie