A.D.
Both my sons were like that at that age. I finally just stuck them in their rooms and let them cry it out. My oldest(now 12) took over a week. My youngest(now 3) took 4 days. I think it is harder for the Moms than the kids. The first few nights I even cried listeneing to them cry. And as mean as it sounds, I also switched the locks on the bedroom doors that way I could lock them in and they couldn't get out. Now my 3 year old stays in bed all night long w/o problems.
Good Luck. I know it's hard.