What Causes Cold Feel At The Back?

hello doc
i am feeling my back cold during evening and night when i try to relax else i am quite weel during days.i feel so cool in my back that i have to wear heavy clothes while others jst have half sleeves dresses.it looks od. my age is 37 no fever and am having this prob from the last one week.i have taken advice of many physicians but no one has any solutiomn. my urealevel,blood sugar(random) cbc and urine test is normal.kindly suggest and solution