Thanks for providing more information.
Firstly as your describe in my opinion,you shouldn't ignore your symptoms and left them untreated as you are suffering from last few months.
And as you have severe pain at different areas so possible causes may include Fibromyalgia,Diabetes,progressive nature of arthritis.
Uncontrolled diabetes or high blood sugar levels can result in pain in legs.
Even high blood sugar levels affect kidney resulting in renal disease and it can be a contributing factor in fluid retention in lower extremities(swollen ankles,lower legs).
Fibromyalgia is characterized by pain to specific areas of your body, called tender points like back of the head,between shoulder blades,top of shoulders,front sides of neck,hips, knees,calves.
So it should be ruled out.
As you have history of Psoriatic arthritis so if you are not taking any medications so it can be progressive in nature.
Muscular overexertion,herniated disc,vitamin deficiencies,electrolyte imbalance are other causes.
So you need to be seen by your doctor for a clinical examination and undergo blood work like CBC,ESR,Serum glucose,Serum electrolyte,Renal function test,MRI of spine for further evaluation.
In the meantime you should take OTC Motrin.
Also do gentle massage and apply warm compresses on back of neck.
And a referral to Rheumatologist should be considered.
I hope this helps.
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