After how many months will my baby boy sleep through the night for the first time?

Varies: It also depends if he sleeps in bed with you or not. You can place him in a crib near your bed. You can use a Japanese Shoji (folding) screen to separate you at night. You can get an intercom from Radio Shack (yes,they still exist) so that he sleeps in one room and you in another and yet you still are connected. Be assured, we all learn to separate at some point and realize that mom will return.