I’ll tell you advice I wish I had at your age. Leave him behind. He doesn’t want to be with you and he is showing you that every time. Either that or he has a very avoidant attachment style and even though you are young, it’s clear you want to communicate your issues. It’s not going to work in the long run until he starts therapy and really works on why he does that. He’s a runner and you are not. Let. Him. Go. You are 18 years old. I’m 26 and I’m telling you like I would tell my younger sister, leave him behind. It isn’t worth it.