Just wanna get this off my chest

Hi, I’m a 19-year-old guy. When I was 16, I saw a girl and instantly became attached to her. I had never talked to her before, and I had never even seen her before that moment. I wanted to talk to her, but I couldn’t because I didn’t know how to approach her or start a normal conversation with a girl.
I don’t know exactly why I’m like this. Maybe it has something to do with when I was in 3rd grade. My classmates used to make fun of me because I would often sit and hang out with girls, and I think that experience somehow affected me and made me uncomfortable around girls later in life.
Since I couldn’t bring myself to talk to her, I searched for her Instagram. It was really difficult to find her account, but eventually I did. I was so happy when I found it. In my head, it felt like I had finally achieved something.
But I never actually got the chance to talk to her. I sent her a follow request, but she never accepted it. She just left it there.
Since then, I haven’t seen her in real life. I only see her profile picture occasionally, but somehow, as time has passed, I’ve become more and more attached to someone I barely even know.
Sometimes I check her profile again, even though I know it isn’t helping me. Sometimes when I’m outside, I find myself going to places where I used to see her, hoping that I might randomly see her again.
And honestly, I hate being stuck in this situation. I know how irrational it sounds. I barely know this person, yet I’ve spent so much time thinking about her. I also blame myself because I never had the courage to simply talk to her when I had the chance.
I just want some advice on how to let go of this attachment and move on. I don’t want to keep checking her profile or hoping that I’ll randomly see her again. I want to stop being stuck in this situation and learn how to move forward.