I Have a Crush On Someone I Shouldn't

I have a crush on my history teacher. He's 20 years older than me and I don't know how it happened but I dreamed of him one night and then I woke up with a whole different feeling. When I see him I feel so nervous. I'm never tired of looking in his eyes.
The last day of school I got him a present and he wanted to hug me but felt confused and awkward so I never got a hug from him.
My friends says that I will forget him as soon as I am out of his class but my feelings are just getting stronger with time.
What should I do?
Pls help