death means renewal,

in order for something to be born it must pass away first,

your liver cleanse is giving you a new lease on life

Looking at these dreams what I see are your fears.

The building could represent self and body.
It sounds like you are in a very desirable building and office space. To me this would indicate that you are basically happy with your body and self.
An office can symbolize practicality, status, accomplishments, and your place in the world. All of which you fear are being taken from you by people that you worked with in the past. So this cleanse seems to be bringing up some old issues. Were there some conflicts then? You may want to review those issues and see if they tie into now somehow.
Are you a competitive person? Just had a thought...
Could you be seeing your symptoms as the invaders? That they are "taking over" your body? Leaving you uncertain of where you'll go from here?

The dream of visiting your own grave shows that part of yourself is dead. I would think the tree is a good symbol,
as it's part of the "natural" world. You fail to mention what type of tree it is. Is it deciduous, or evergreen? Does it have leaves? Are they green or fading into autumn colors? Is the tree healthy or not. All these things would be clues as to what the tree represents. It could be a symbol of the soul that dies only to be born again. It could represent your family. How do you feel about the tree?

Hope these observations help.
Marj