S.S.
We went thru this when my kids were little. we did the gate thing. it is hard and they will cry for as long as they get the attention that they want. ignore it. don't shut your door. just keep saying mommy is sleeping go to sleep. something you could try though that we did. (read it in a magazine or board like this lol) was my husband took the broom in and "swept out" all the scary things from under the bed and out of the closet. of course there was absolutely nothing there but it was the concept. so we did that and it lasted a long time but eventually it got to the point where we didn't have to do it anymore.
S.