6yr old has pain in feet and knees (sometimes severe pain)and pos ana and high esr. no swelling. was told from being flat footed could this be true?

Unlikely: With severe pain and inflammatory/autoimmune markers (ana, esr) i'd worry more about systemic conditions like jia. You should be seeking urgent medical attention for this.

Not from flat feet: Given nonspecific nature of ANA and sed rate (esr), more studies are required to make a definite diagnosis. Absence of joint swelling virtually rules out the possibility of juvenile rhematoid arthritis.

Have child evaluated: I would not so easily dismiss the positive ANA and the elevated esr. I urge an opinion from a pediatric rheumatologist. Sometimes joint inflammation can be subtle and missed by a physician.