It's normal.

Experts think it has something to do with normal neurological development, and it's a phase that many babies go through after an initially peaceful newborn period. Don't worry, it will pass! Just hang in there, and grab a snooze here and there while you can. The thing about the first 6 months of babyhood is that almost everything is a phase -- it should pass. As distressing as it is to see your baby crying around the clock, just take comfort in knowing that you're doing everything you can, and that your baby will eventually turn the corner.