Help-my son has suddenly become afriad to sleep and is really anxious

We bought a new video monitor 1mo ago, w/ intercom and I used the intercom to tell my 2.5yo son to get back in bed. It scared him to death, he came running out of the room, crying/screaming. That same week, he came down w/ a fever for approx 4days and was hiding under the covers, not sleeping and crying alot. I thought it was the fever, but after the fever was over he still hid under the covers. I took the monitor out last week b/c he would say things like "the monitor can't hurt you". He used to be a great sleeper, loved his bed, would lay in there and talk and sing. Now he becomes really anxious when eating lunch or dinner before bed. I need help!!! He will fall asleep w/ covers over his head, after about 45min, he'll wake up crying. If I go in and try to comfort him, he will just be overtired for the rest of the day. I've let him "cry it out" for over 1hr too. Thoughts? I want my good sleeper back!!!!!