For those of you who are familiar with autoimmune disease there is a test known as ANA that identifies whether you have antibodies that are attacking your system or not. 

I am a 31 yr old male who eats very clean paleo, works out a lot and generally take care of myself. I do work a lot and tend to be stressed out about that but otherwise I am healhty. I have been feeling very fatigued and weak the past month and after going to my doctor to get numerous blood test taken I found out I tested positive for ANA. All other tests came back normal but my ANA (anti-nuclear antibody) panel was positive, but the titer was so
low (1:40) that my Dr does not suspect any auto-immune disorder or connective tissue
disorder. Moreover, the rheumatoid factor (RF) and C-reactive protein (CRP) and
ESR (estimated sedimentation rate) were all negative, so there is no
inflammatory process either.

What gives? What else could this be?