If your doctor's note is for bed rest you can do FMLA family medical leave act. And they have to keep a job for you it just doesn't have to be the same Job.
I have heared that the flashing and blurryness in the eyes can mean high blood pressure, which it sounds like from your Job could be the case. You definitely need to find a way to destress, I would talk to your doc if I were you, explain how your job has been effecting you, and your symptoms, they may want you to take a break from working, on which case they would provide a note, and at that point if you got fired from your job you could sue them for that. Its illeagle to fire someone with a medical need like that. They are forced to put your health first