Yeah it is better to be truthful than to lie. Lying will cost you sometime down the road if not now. If the Immigration folks ask you why you worked without papers., just tell them you had to pay your bills. They know people work under the table all the time. And especially if you have filed your taxes, it is better to come clean with them. Believe me if they really want to find information about people, they have every tools to do it. It is just that Immigration turns a blind eye to folks working under the table coz it helps the American economy. This is my two cents.