Mine is under 20 also, but I feel really unwell. I have Lyme and several co-infections. I have several bands positive on IgG and IgM.
Is your doctor going solely by a negative test to determine that you don't have babesia? It is my understanding that the babesia tests are not accurate. Do you have a LLMD?
I would not base treatment solely on the CD-57, but from what I understand, a low number is associated with chronic Lyme and makes relapse very likely. With symptoms of fatigue, sweats, etc............I would look into it if it were me before things become worse. Did you have the CD57 done when you first got sick in 2009? When I had mine done I was very sick after a severe flu a few months earlier. Because it was so low, several LLMD's said that I must have had a re-infection because there was no way for it to have dropped to that level in a short time frame.