Sleep

I’ve been exhausted!!! My son sleeping has been soooo messed up lately. He was typically sleeping 12 hours a night but now he wakes up almost every night at 4am and cries until I put him in my bed to sleep with me. He seems very uncomfortable I have him sleeping in the dock a tot grand during the night in the crib. Any suggestions on what I can do? Any one else having a hard time with sleep?