Why can't i move on from my first love?

we met on a dating app and hit it off almost immediately. there was just something about that first spark that made me feel like we were eventually going to end up together. We were in a long-distance relationship because i was in college a few states away from her while she was in college in another state but everything about us felt like the timing was right.
We started dating after only a few weeks of talking and at the time i honestly thought we were inseparable. Unfortunately my 22-year-old self wanted to explore the dating scene more and that ended up costing me the relationship. We broke up but within two weeks we got back together because no matter how much i tried talking to other girls i couldn’t stop thinking about her.
We stayed together but the distance slowly started taking a toll on us. We decided we would try our best to see each other at least once every six months. We had never actually met in person until that first six-month mark.
I went to see her for her birthday after her finals were over so we could spend as much time together as possible. I still remember our first hug and the tears of happiness when i surprised her by arriving two days earlier than i had told her. Seeing how happy we both were in that moment is something i’ll never forget.
We continued dating and eventually almost two years had passed. Even though we loved each other we had only been able to see each other once during those two years and i knew the distance was getting harder for both of us.
Then i made one of the biggest mistakes of my life.
My dumb 22-year-old self got it into my head that she should have been the one making the effort to come see me. Instead of communicating that with her i kept it to myself and waited for her to bring it up. When she eventually went to a party with her girlfriends and kissed one of them i got angry and decided to break up with her.
The worst part is that i had already told her i was completely okay with her doing that.
I turned completely cold after the breakup. I was lonely and heartbroken but somehow i convinced myself i was fine and moved on within a week. I acted like i didn’t care and i have no idea what she went through during that time.
And now it’s 2026. Six years have passed.
I still think about her every single day.
There hasn’t been a day where something hasn’t reminded me of her. A song a lyric some tiny thing she used to do and suddenly i’m right back there feeling everything all over again. I’ve dated someone since then partly because i thought being with someone else would finally help me forget her but it never worked.
She somehow left a place in me that nobody else has been able to fill.
I eventually tried contacting her because i wanted to apologize. I wanted to take responsibility for how badly i handled everything and tell her how sorry i was for ending things the way i did. She blocked me.
I’ve heard through her friends that she’s been dating someone and now i feel completely lost. I know six years is an incredibly long time and i know i probably sound crazy saying this but some part of me still believes she is my person.
I can’t imagine marrying someone else. I can’t imagine loving someone else the way i loved her. I’ve tried to move forward but she still feels like the person i’m supposed to end up with.
If she called me tomorrow i honestly feel like i’d be at her door in a heartbeat. No questions asked.
i don’t know what to do with these feelings anymore. Part of me is terrified that if i don’t end up with her i’ll never marry or love anyone again.