Suggest Remedy For Joint & Hip Pain

Hi. I have a fairly complicated scenario which I d appreciate some guidance as to the underlying reasons for my symptoms. Symptoms: Joint Pain (hip, shoulder, knees, spine), Consistent Swelling in my Achilles Heel, and general fatigue. X-Rays show some minor joint damage in my hip. Had days of intense pain as a result. I have been diagnose by a rheumatologist as having psoriatic arthritis. Currently taking sulfasalazine (3000mg) and proxicam (20mg) daily. Maybe I m just in denial but I would like to test an alternative theory on why I may have these symptoms. I have realized I have been under eating for about a 2-3 year period. My daily intake of calories apparently should be around 2500-2800 Calories a day. I would be lucky if I had more then 2000 daily and would consistently have less, which has been the case for many years. I bottomed out at 65kg, which is quite underweight considering I m 180cms in height and Male. Before I had any symptoms I was going to the gym about 5 days a week and was doing pretty intense workouts which I also did for years. My question is, could my symptoms be caused by my diet? I have been diagnosed with psoriatic arthritis, however is it possible that my long term undereating has manifested in a way that would be paralleled by this disease? It is a clinical diagnosis, therefore it s hard to know for sure. I ve had various blood tests which are indicative of this disease through ESR and CRP blood counts. Can undereating long term raise these blood markers?