I fainted at work and that caused fracture of my spine and right shoulder. I lost my job while I was recovering. What can I do?

On 8/11/15 I fainted at work while I was on break. I lost consciousness for several minutes and had fracture of lower spine and right shoulder during the fall. HR representative called 911 and I was administered at ER. While I was recovering I was working as well. Some 2 months ago my spine doctor recommended working from home. My employer wasn't very happy about that, but I needed to work and heal at the same time. I was delivering on my work, but my boss happiness that I'm working from home was less and less. Finally on 12/21/15 I was called to my office to discuss my performance and regardless of my accomplishments and the fact that I was still recovering, I was almost forced to sign that I'm resigning from my job. Other option was 30 day non-stop monitoring and coming to office although they knew that I can't do that and that will result in being fired. Do I have any right to sue my employer? They even didn't allow me to use short-time disability that I mentioned to HR.