I like a guy in my class and I stalk him
Are you finding something new about the guy?
I just want to know everything about him, what he does, who he spends time with
That is a bad thing for you to do. It is wrong to stalk people and you could end up in a lot of trouble. You will also give him a bad impression of you if he finds out what you are doing.
If a guy like me he don't have to know what I'm doing.
That's the opposite. If a person likes someone. That person would want to know what you do all the time, OMG, that's what you're doing.