My Head is a horrible place to be.

What does it mean, to feel numb?
Is it when you're conscious but hardly lucid? Is it when you just can't be bothered to think or feel, or in fact do anything at all? Is it when you feel bored or tired and don't really follow reality, or an underwhelming mood when you don't quite feel happy, but don't quite feel sad? Is it when you just can't concentrate or focus on your daily tasks? Or is it when you feel nothing - you don't feel anything at all.
Because if you don't feel anything at all, how could you feel numb? Doesn't it require feeling to know that you are feeling numb? How could 'numb' be a feeling if it involves having no feeling whatsoever, and the actual 'feeling' is that you feel nothing?
And if it is a feeling, How could a feeling that feels so strong, have no definition.

Maybe there's no such thing as feeling numb. Maybe there's no definition because there is nothing to define. It could just be one huge contradiction of itself, a learnt expression of the human mind that doesn't actually exist. Maybe being numb isn't a result of having no feeling, but not Wanting to feel. If this numbness just had a simple definition, it would makes things a lot easier. If people like myself could just be given a simple, clear answer to the question of what was going on in their head, then it would save a lot of internal confusion, and end this random query/struggle in my brain. All I would like is just some answers that explain this feeling of not feeling.