Has anyone ever checked your immunoglobulins? You know, IgA, IgG, etc.

If you have a low IgA, a celiac antibody test can look normal when it's not (false negative).

If you have a low IgG, it's the same with the MG AChR antibody tests. I believe MuSK is IgG too.

Some people with certain low Ig's have problems with infection. Maybe yours are fine but it's worth checking.