I need help!!!!

So, there's this guy that I'm going to call E.
I've always known of E and we saw each other a few times because we're family friends, but I only really started to know E this time in 2022. I texted him first, and soon it was like we were best friends. We texted every day, facetimed at least once a week, played video games together, and we were inseparable. Soon, I developed feelings for him.
I tried to hide it, tried to continue the way we were, but it became too much. I told him, and I felt better when he said it was okay. He didn't tell me he liked me back, but he didn't tell me he didn't like me back either.
There was a period of where we became more than friends, and we flirted, told each other we were in love with each other, and he even called me Mrs [his surname]. I was head over heels.
We had made a plan to meet up in February of 2023, and when I texted him the week before to confirm the day, he told me he had a girlfriend. I was heartbroken. For weeks, I would stay up crying at night, I had never felt such pain. I've always had little crushes here and there, but I was in love with E.
His girlfriend followed me on social media, and when prompted, told me that they began to date in December 2022, 2 months before he stopped flirting with me. I was horrified. I thought he was mine and I thought I was his. I was wrong.
Two years forward, they're still dating and I can't get over him. I can't go a day without him on my mind and it hurts so much that I'm still in love with him. My brain knows that I can't be with him, but my heart is holding so tightly onto hope, I'm scared it'll never let go.
What do I do?

you need to process it and heal otherwise you'll be stuck in this limbo.

how do I heal from it?