This isn't a herx die-off, it's the symptoms of candida overgrowth.
Highly discourage use of protein shakes, it will stress out your kidneys and other organs.
You can eat chicken breast, yes.
In my opinion, you need to begin eating raw salt-less sauerkraut immediately to heal this. Look on youtube for how to make it, it's very simple and can be done with only cabbage.
Candida has many symptoms, that can disable a person no matter if they're a bodybuilder or not; my guess is your system is under lots of stress from your diet and this will need to be resolved for the real herx reactions to begin.