I have an unhealthy obsession with a classmate
Is this true? Can you describe it to me?
I can't describe it with words, but it shows through my actions.
I think you should try to be conscious of when you do things that show obsession with your classmate. It's not healthy to act that way.
How do I let go of this obsession?
You can try therapy to get some help. There could be other reasons like ADD or obsessive compulsive kinds of disorders.