I’ve been meditating for years and completed multiple Progress of Insight cycles. 

I’m now in the situation where I’m extremely depressed and anxious and it feels as though my chest is completely empty of self and hollow and ‘dead’ and it’s extremely distressing and disconcerting. Could this be related to having Borderline Personality Disorder and a 'weak ego'?

Has anyone ever heard of this before or have any idea what’s wrong with me? 

I’m sorry for posting here but I’m desperate

If you are desperate, it really is best to consult directly with people who are trained and skilled at these kinds of questions/problems.

I googled mental health support:

Crisis Text Line | Text HOME to 741741 Free, 24/7 Mental Health Support

National Hotline for Mental Health Crises and Suicide Prevention | NAMI   

Please reach out to those that can help you to directly work on your anxiousness and depression. 

I agree with shargrol.

I am not a psychologist but since you posted here, I suppose you wanted the kind of advice you are likely to get here. So I'll give you some.

Firstly if you think meditation caused your problems, maybe you should stop doing that kind of meditation and try something else.
I recommend relaxing meditation. When I am fully relaxed, nothing bothers me.

Secondly if you are not eating a healthy diet, I suggest you start doing so. If you are vegetarian or vegan try some meat. Avoid caffeine, alcohol, nicotine, excessive amounts of sugar, and recreational drugs. If you have a heavy addiction to, for example, caffeine or something else, it might be necessary to reduce use gradually, but try to get off it.

Hello!

First, I am sorry if you are feeling distressed.

I guess these are my thoughts:

Have you ruled out medical causes for the new sensation?

If there is no medical cause, then it might just be transient mind-body stuff. 

Can you be curious about it without labeling it? Can you notice your reactions to it? (I'm feeling afraid of this feeling, etc). Was there a trigger for the feeling? If you drill into the sensations what it's like? Numb? Cold? Dense? Big? Small? Etc. What about the feeling is upsetting? What meaning do you assign to it?

I used to feel (for years) like I had a void in my chest. I know that sounds strange. In my case the void feeling went away by doing metta meditation. I imagined a small candle and summoned a feeling of love and goodwill and sent it to my chest. Over time the void filled in. Now it feels like there is no hole there, just a sort of glowy love feeling of comfort. Not sure if this helps. But I had a similar (maybe?) feeling for many years that also upset me. It got better and went away on its own when I started heart practices.