Am I depressed??

Hey, I just joined. I live outside of the US. I don't have any friends where I live. I pretty much live in an old person town. I've been doing pretty good until I met my best friend in the States for a week. The second I came back I immediatly felt unbelievably sad. Now I'm back to my boring life where nothing brings me joy. I have to continue school until I'm finished for the year. Even if I finish school, what's the point? I'm going to end up being even more bored. The internet is getting extremely stale. It's the same thing every day. Everything that had brought me joy when I was bored now doesn't. After being three weeks clean, I decided to cut again. But just because I cut doesn't mean I have depression right? I don't feel worthy of having depression. I have a great life. Why am I possibly depressed and not a homeless dude. I just don't know. I feel hopeless.