21 month old waking up at night screaming/crying

[slworld]

DS has been sleeping in his room since end of Nov (before that he was sleeping in his crib in our bedroom). The transition was pretty smooth & we didn't have any issue until a few weeks ago. He started waking up about once a week, usually early in the morning (between 2-4am). He wakes up crying/screaming really hard and won't go back to sleep until we bring him to our bed. We tried to ignore him for a while to see if he will settle down on his own, but that doesn't seem to be happening. He wike up twice this week. Neither DH nor I get any sleep with him on the bed (he moves a round a lot & literally pushes me off the bed, and we have a king bed!). Sounds like night terrors or nighmares (not sure what the difference is). Any suggestions on how to get him back to sleep in is crib when we he wakes up. DS sleeping on our bed is really not working for us.

Thanks much