Anyone can explain this?

So when i was in high school this guy liked me and its kinda annoying. I don’t like him back and actually kinda avoid him although we’re in the same class. But when graduating i apologize if the way i act offenses him. move forward, i always think about him, like picturing his face in my thoughts a lot since then, but not in a good way. I felt anxious when thinking about him but couldn’t stop. I can differentiate the feeling of denial of liking someone and being just don’t want to do anything with someone. Even in my dream when he appeared, i always feel like “no” i don’t want him in my life, and i can't even feel a slight of liking this person. I always overthink and fear i ended up with this person because of that. It makes me feel restless. Anyone know whats going on and do you guys have any opinion or maybe advice for me?
Anyone can explain this?
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