Night crying, what's wrong?

Kimberly
So my 1 month old for the past 4 nights has been crying none stop. He has his days and nights mixed up so during the day he's asleep mostly bit when he is awake he's very happy, no crying. But once he's awake for his long stretch, which is around 5-6 hours he just wants to eat and cry. He's not colic, he burps and passes gas just fine all day, no teeth coming in what could it be?