T.B.
Oh my...poor little guy. I have a couple suggestions here. Does he have a night light? Try and get one of those fun ones that make shapes all over the walls. Try sitting in his room for half an hour each night after you put him down. Take a book with you or something to entertain yourself.
Sounds as tho he is genuinley scared. I wouldn't want to start a bad habit of letting him sleep with you. I know I made that mistake and it took until my son was 4 to get him out of my bed. Also....he could be getting his molars, that would definatley be the cause of his pain. Check his mouth.
Good luck.