how do i get over him?

it's been 5 years since I made the mistake of leaving my best friend. I regret it every day. He reached out to me in November and we are still best friends. But since the day I left all I've done is regret it and can't stop thinking about him. He knows and he still loves me like I love him but he's so hurt he will never take me back. today's been the worse. every song on the radio or post I've read makes me think of him and us. I can't stop picturing me laying on his chest listening to his heart beat or him singing to me or laying on the grass at the park looking at stars. it calms me so much. I have really bad anxiety but it always relaxes me to think about that. he told me today he was thinking about us looking at the stars and naming constellations too. he got into a serious accident and almost died the other day when his sister's truck caught fire and it scares me to lose him. we don't talk much cuz he doesn't have a phone right now but he makes sure we talk at least once a week. everything about him is perfect. I miss him so much but I know I screwed it up by leaving. I left because I was scared because it was so perfect. we still call each other soul mates and best friends and we talk about when we were together and it just kills me. what have I done? he's so amazing but we can't be together. weve been through so much. I've known him 15 years. how do I get over him without losing him? I will never stop talking to him. he's the best thing that's ever happened to me and I won't give that up again. I just want to stop hurting and hating myself.