Erythrocyte sedimentation rate (ESR or "sed" rate) is a test for inflammation. An elevated sed rate generally means some kind of inflammation was found, but doesn't point to the reason why. It can be everything from an infection to arthritis to lupus to many other illnesses.
It sounds like they are testing to determine why you have joint & back pain, and why you are tired. There are multiple illnesses that can cause this combination of symptoms. My first lupus symptom was fatigue...but it was more than just tired...I was exhausted after 10+ hours of sleep!
You didn't mention what kind of Dr you are seeing...if your general Dr runs out of ideas you probably want to see a rheumotologist.
Meanwhile, take a look at your food - nutritional & supportive of good health? Not too much sugar or too little protein? Eating at regular intervals? Check your sleep - do you sleep calmly, all night, or is your sleep interrupted? Try adjusting light, temperature, etc. Exercise -- are you getting too little or too much?
Do some reading at
www.lupus.org if you haven't already. Come on back with specific questions & we'll be glad to try & address them!
Best wishes,