How do you know if you have depression?

I’ve looked up the symptoms and I’ve got almost all of them, but I don’t want to self diagnose and I don’t want to go to a doctor (or tell my parents for that matter) and I don’t know what to do anymore

Sometimes I am emotionless and just want to sleep or lay there for days on end, other time my mood changes like there’s been a dial spun every few minutes. Sometimes I’m happy I guess but overly happy or just there in the moment. I don’t know if this is some sort of mood disorder or something like that but I have been going through some stuff with my sexuality, friends, family, problems with myself and I guess you could say it’s a phase but I don’t think so

So I would love to here opinions because I’m lost at the moment :/