Missed out on childhood

17 m I can’t stop thinking about how much I missed out on. When I was 12 around year 6-7 at school I had so many friends. I was so happy just being a kid doing random shit having fun everyday day seeing friends. Then at 13 at the end of year 7 I had to leave school. After I left I had no friends no one to talk to no one to see. After 2-3 years when i was 15 a girl I used to go to school with messaged me and we eventually started dating. Then that ended after like 3-4 months and I was completely alone again. Now im 17 and in college but dont really get on with many people and just miss being a child. Everyone else had a chance to grow up with friends ect and I was just alone. I feel like I missed out on so much and feel like im still a kid waiting to grow up when everyone my ages has already been though that and grown up. What should I do ? I can’t stop thinking about this.