aso titer

I've recently had my aso titer drawn again, and it is still over 400. I first started being tested 7 years ago.  They thought in the hospital I had strep , but later I was sent to a infectious disease specialist and he told me to keep a watch on the titer. No one has given me a answer of what causes this to stay elevated. I've had numerous problems with fatigue and mouth sores but , even when no symptoms are there the titer is still high. Is there a explanation for this? Also my tonsils were removed when I was 15yrs old. So we know that is not an issue. The infectious disease doctor 3 years ago had no answer other then for me to not take any antibiotics unless it was a confirmed infection. Hx Epstein Barr dx in 2000!