How do I ask for a month off without her thinking I want out?

Work has gone badly wrong, I am sleeping about five hours a night, and I do not have the capacity for anything that requires me to be present for it. That includes this, which I otherwise love.

The problem is that I know how how do you feel about taking a month off usually goes down, because I have been on the other end of it in a previous relationship and it is not a neutral sentence.

How do you ask for this without it landing as the beginning of the end?