I would suggest starting with your Primary Care Physician (PCP). Your PCP can evaluate what is going on and refer you to the appropriate specialty.
As far as Multiple Sclerosis: MS is not a disease of the joints. Has a Dr. suggested MS to you?
Diagnosed with Multiple Sclerosis in 1985
PTSD diagnosed Feb 2004 (PTSD since age 2), Anxiety/Panic attacks secondary to PTSD.