What to do with my status situation?

I'm 19 I'm suppose to be getting my green card through my stepmom who is an American citizen she is doing my papers my dad's and my sister's. when I entered the U.S they did not stamp my pport but they stamped my sister's and I do not have an I-94 form. My lawyer is trying to prove that i did indeed enter the U.S legally, but if he fails to do so I wanted to would marrying a U.S citizen change that? My boyfriend and I were already planning to get engaged during thanksgiving and married in January because we thought I would have my green card by then. We were wondering if getting married sooner would help my status situation since we were already planning on doing it, why not do it sonner?