This is like a cycle I find myself going in and out of and I think a lot of people out there do the same. How to you combat stress if you are stressed over hair loss to stop the stress from causing more hair loss!? It is like an annoying riddle!
It may be that stress has a minor effect on hair loss, whereby it accelerates the progress. Even if that is so, it probably won't be a positive-feedback loop that grows exponentially, but rather one that plateaus.
There are two ways to combat stress from hair loss. One is to focus on other issues, the other is to defeat hair loss.