Mental health and sense of belonging

I'm trying to find the root cause of my declining mental health. Maybe there isn't one. Maybe my brain is just physically broken and I have to deal with it.
But what I tend to think of recently is the concept of belongingness.
I rarely feel I have a sense of belonging anywhere. And my theory is that the constant otherness is what is causing the degradation.

So what i want to is, for those who experience frequent depressive cycles -- do you have a sense of belonging? Or do you too feel constantly othered?

(I hope this makes sense haha)