I have no idea what to name this. Um missing something that isn't even there?

Do you ever feel like you're missing something, or someone?
And all your happiness is gone, all your joy, all your fun?

And the worst part is, you don't know what's missing, or if anythings missing at all.
So you're sad, depressed. You let yourself fall.

You try to fill this....this gap with things, objects you don't need.
It's this kind of hunger, hunger that you need to feed.

But the gap is still there, no matter what you do.
And you don't know how to get rid of it, you don't have a clue.