I relate really well to your post, except weirdly I have never actually felt this sensation as one of 'emptiness'. The metaphor has never resonated for me and so I have often assumed I do not have this particular issue. Only I think I do, but experience it differently. Perhaps it is more a feeling of iciness at my centre. And sometimes even iciness across my skin (and can happen even when I'm really hot). Also a feeling of being incurably separated from everyone and everything - and this can happen even when I'm being embraced by someone! Like there is a metaphorical ice wall that won't melt...

What has helped me as others have mentioned is a kind of 'self love'. I haven't managed to achieve this in a stable and ongoing way but I do manage to experience it, episodically. The way I do this is with a kind of triangulation. There are people and even pets that I ADORE. Their value is immediate and undoubtable to me. What I do is summon up these feelings and then deliberately redirect them to myself. It's not always effective but it sometimes is.