I think you're really strong to be going after your PhD! That is a huge accomplishment. I wish I'd had the conviction to even try. I really did want to be a psychiatrist.

I wanted to because my cousin has schizophrenia and I wanted to help people. But, I didn't even make it through my assosiates degree. So, I think it is amazing what you have accomplished!
I know for a fact that when I dropped out of college I was fully intending to go back. I never did. You know those comercials where it says "life comes at you fast" and like one second a kid on a swing is 5 and then suddenly he's full grown.... well, that is life....

Why am I not still 19? I was only 19 yesterday. And that is a huge regret for me that I "gave up on myself." I often feel like a total failure. I'm a secretary. I'm too smart for my job yet I struggle at my job. It is hard to come to terms with. Of course, I didn't drop out because of my health, (although it was just it wasn't to make myself better it was the direct result of being ill, I thought I was far too stupid to finish school.)
So, I think if you need to stop for your health, you need to first acknowledge that stopping for your health isn't being a failure. You have to do what is right for you, and that it is the right choice. And if you are unable to go back, that it isn't a reflection on you in a negative way. If you can go back, then that's great! Don't work so hard you make yourself sick.
I hope whatever you choose you realize that you have done a great job so far already.