You're an angel of the Lord... or, at least, you used to be before you defied Heaven for Sam and Dean. Mainly Sam.

Sam had just recently released Lucifer from the cage, and you and Castiel were trying to help Sam and Dean put him back. But... you and Sam slept together... a lot. And since you were an angel, neither of you believed you could get pregnant. So, you never used protection.

But... little did you guys know, your human vessel could get pregnant... meaning you as an angel could... and you did, but didn't realize. You began slowly forming a bump, suddenly began eating human foods, and you were disgusted by the simplest things.

You were now four months along, but since you were an angel, you had no clue. You just thought there was something wrong with your vessel. Sam hadn't taken notice because you always wore a hoodie that could hide the tiny bump... that was until you were both on a walk through town during a case, and your hoodie rode up slightly... revealing the four month bump...