Hi ShyGirl, the only person who can answer you about the test is your doctor. Have the test done and ask him/her what it is that they are testing for and why they are doing it again. Also ask them what they are going to do if it comes back with any reading that isn't 'normal'. There's no point putting it off as you will worry over not having it done.
ShyGirl - it's a nuisance having to have those tests done, sometimes we feel like a pin cushion, then the wait and worry until the results come back.
You are not feeling so good, so its best you have this test done, your doctor is trying to find out the cause of your health problems. The ESR test is done to detect inflammation in the body, you can read about it here: http://www.patient.co.uk/health/Blood-T ... mation.htm