Sam had accidentally knocked you up. Though this wasn't necessarily a bad thing, the timing wasn't great. It had been a week before Dean died and went to hell.

So, the first four months of your pregnancy, the four months Dean was dead, Sam had disappeared. Little did you know he had been working with Ruby to hunt down Lilith. He was also guzzling demon blood. Once Dean had been pulled from Hell by an angel named Castiel, you and Sam reunited, and he decided to pull his act together and be there for you.

So, he was there for the next few months, practically living a double life. He was guzzling blood whilst also taking care of a newborn. Though he loved the baby with all of his heart... and you, it was all taking its toll on him.

So, one night in the motel room as you slept, he snuck back in after a meet-up with Ruby to get more blood. The baby was fast asleep in their bassinet that sat next to the motel bed... he sleepily... and tiredly snuck back toward the bed...