You have a difficult choice. One of the things you can do is write out a list of the pros and cons of going back into sales vs going back into teaching (or a different field). Or, does your gut-level intuition lead you in one direction or the other?
I am heading back to my job in one week after being out for a month. I was just diagnosed with bipolar disorder and hospitalized for 2 of the weeks. I'm a little nervous about returning to work, explaining why I have been out to my coworkers and clients, and trying to keep gains I've made when I blend work into the mix. So , I can empathize with you. Good luck with your decision.