I was the one left behind. I went to an international school where people who moved around every 3-5 years put their kids, and I always gravitated to them, because they were always the most interesting. They were always the nicer ones, too.
Seeing them leave one by one broke my heart. I decided to no longer have friend in my teenage years.
Anyways, the point is: there was something to be broken for me. There might be anchors you aren't seeing. Maybe you can regain contact with some older friends? Maybe you can try to put your trust in a friend you had in one of those schools?
The other point is: I've regretted cutting friendship from my life in my teenage years. The phasing out of that was super awkward, and sometimes a bit humiliating to be honest, but that's where I met some of my best friends. On the other hand, I don't regret any of the stupid stuff that came out of my mouth as I was clumsily stumbling out of my shell, even when I unintentionally hurt people or made a fool of myself, because it was what I had to do to connect with people. I fact, I'm proud for that boy.
I've made fantastic friends here but i'm moving in two months, It's kinda scary