Teaching and feeling crummy; it happens. How to deal?

I often let the kids skip on school work when they are particularly sick. Runny nose? Coughs? Even a slight but bearable fever? Well I think they are still capable of doing work in those conditions. I at least take it easy on them in those circumstances. But when they are truly sick they get to lay on the couch and watch T.V. and forget school work all together.
Yet when I'm sick...well often it's business as usual. Lately I've been struggling with feeling sick especially during the middle of school time. Head pounding, arm aching, leg asleep, and just feeling disconnected, I blurrily manage to instruct the kids. After all, I'm not running a fever, I'm not throwing up, etc etc. so I do not meet the criteria for skipping school or allowing the kids to do so. So we plunge forward.
Yet at night I lay there aching and twitching and not sleeping except in little patches. Patches which consist of strange and evil nightmares. Last night as I struggled, I finally fell asleep. I dreamed I was driving up a hill and I could not, for the life of me, keep my car on the correct side of the road. All along the road were beautiful blossoming trees but beyond that the sky was dark and cloudy and there were hundreds of cars on the opposite side of the road. As if everyone were making a mass exodus in one direction and I was the only person going the direction I was. I swerved and couldn't understand why I couldn't drive straight, nearly hitting and luckily missing, car after car. Finally I stopped at a stop sign. One of those four way stops you know. I couldn't control myself and went at the same time another car went, nearly hitting him. The guy backed up and blocked my way with his car. He got out and got in my face. I was crying, apologizing, and trying to tell him to go away. He was saying he was going to kill me for cutting him off. I gasped and tried to drive, but his car was in front of mine and suddenly trees were surrounding me every other way. His hand was reaching through my cracked window to grab me. In that moment I felt my phone in my right pocket positively jabbing into my thigh. I would call for help! I reached for it, trying to dig it out of my pocket but the more I tried to grab it, the deeper it lodged itself against my thigh. As if it had a mind of it's own. It was hurting me and soon I was afraid it would burrow deep inside my leg. I started crying and finally I awoke to the sensation of my thigh siezed up in a cramp. Right where the phone in my dream had been digging into me. So now...I feel like I can't escape whatever is wrong with me even in my restless sleep.
I haven't been to the doctor yet, but I do have an appointment. I have two fears. One is of being diagnosed with something terrible (unlikely of course but one can't help but think such things. We are all human after all.) Another is them finding nothing wrong with me and I have to go on like this with no way to make it better. I suppose it can't last forever. Best outcome? Finding a minor issue that can be easily fixed. That's what I hope. I want them to find something...so it can be fixed.
So, going through all this has made me wonder, how do moms/teachers cope when they are faced with a chronic condition. Like chronic pain, MS, fibromyalgia, arthritis and the like. I know there are moms out there living with these issues that still manage to homeschool. I'm not saying I have any of these conditions, it's just that my current situation has made me ponder on the subject.