My son is 12 months, and like clock work he is waking up at 2am every night, why? He's screaming..?

Is anyone else going through this? He''s just started doing this a week ago? I don't know what the problem is.. I change his diaper, and feed him milk, I try to rock him.. give him his pacifier... nothing helps. He's screaming right now... I don't know what to do.