Speaking as a medical professional.
Please consider taking the medication he gave you unless it's Ambien, then tell him to shove it up his ass and give you a low dose of Ativan.
Ambien is a dangerous drug, and I'm honestly surprised it has been pulled off the market, and suspect one day it will be, as soon as the drug manufactures come up w/ a better one.
However old school anti-anxiety meds taken by someone who is cautious with them can bring you some peace.
Cortisol levels rise in any fight/flight situation, but they can remain elevated for ongoing trauma and stress (insert picture of NorthernMSB here). The caveman brain response to those elevated levels, and fight flight is being unable to eat, that was so we could run from dinosaurs and tigers, to stay alive, and not be weighed down by full tummies. However extended periods of being unable to eat cause significant malnutrition (studies have shown that a body under stress without nutritional supplementation can go into a starvation mode within 48 hours - That's why we put feeding tubes in patients in the ICU within 24 hours if they are unable to eat.)
Amyway without proper nutrition you get fun things like anemia, brittle nails, hair falling out in handfuls, overall decreased immune function. Guess what those aforementioned pills to help you sleep do?
They let you sleep, which resets the cortisol hormone pumps, and it allows you to eat again, which in turn helps your anemia, your hair, and most likely your other health issues you are experiencing.
I get not wanting to take stuff, I was that person too. I was resistant to meds for most conditions I have encountered, however as I am approaching 50 I have fully embraced the whole "Better living through Chemistry" belief.
My period of fight/flight lasted in total about 6 months, with a 50lb weight loss. I had hair falling out, and while in it, I also got to experience an autoimmune response that has resulted in psoriatic & inflammatory arthritis.
Please consider taking meds to help yourself. You need to make you the priority.
The feeling flat? That's your brains way of saying your body needs a break from the bullshit you are dealing with, and like me, you choose to throw yourself into your work so that you use that fight/flight energy, and still keep the monsters of infidelity locked in the closet for the most part.
Don't. It's not healthy, and you will eventually crash and burn.
PLEASE PLEASE PLEASE make you the priority, and if you can't eat, drink some protein shakes muscle milk is really tasty. Make sure you are getting at least 5 hours of sleep 3 nights a week. If that means drugs, then do it.