(1) the alien, on the date of filing an application for adjustment of status, is present in the United States pursuant to a lawful admission;
(2) the alien, subsequent to such lawful admission has not, for an aggregate period exceeding 180 days--
(A) failed to maintain, continuously, a lawful status;
(B) engaged in unauthorized employment; or
(C) otherwise violated the terms and conditions of the alien's admission.
So,if you ever worked without EAD/working visa ,or did other things violated condition of your status,you can't adjust your status except you marry a US citizen