How the FUCK do you get a drs note for having too much anxiety?

I came into work today full of anxiety (short breath, feeling like I'm about to throw up) and said if I need to leave, I will. I was told I can't leave unless A: I find coverage (I don't talk with my coworkers much so not possible) and B: to have a Drs note. How do you just go and get a note saying "8bitgamer757 had too much anxiety today so he's fine to be home"???? I need to get out of this shitty dishwashing job, it's tearing my body and mind apart.