I hope you are reaching out to people in your life and getting help.

I suffer from depression and have bad periods, when I do i will inform my Dom about it and take a step back. Just as if he's having bad days (stress from work or anxiety) he'll inform me. Its normal to not always be able to perform, as long as you're honest and upfront, the other person should be able to then readjust.

Dom tends to cook/buy takeout/snacks and we watch a fun show when I'm doing bad and if he's not ok, I always offer a massage and snacks. Also we are both very open to talking about our issues to one another.

I understand it might be harder for a Dom/Daddy (even simply a man) to open up about their struggles because of their role and societal expectations but at the end of the day it's still a relationship/dynamic. You both need to engage in it enthusiastically and when you're not feeling it that is not possible and that's ok.