late period with a loop as birth control and pregnancy test

hi..im 2 wks late for my period its the first time it happen since i inserted the loop 1 and half year ago..i did both urine and blood pregnancy test both negative..im feverish,always tired and stressed out as if im having PMS but no bleeding till now any one can help plz??why is it late since no pregnancy?and im not on diet or less active than my nature but i do have some social problems with my iinlaws???(who doesnt ;>)