WARNING: SENSITIVE TOPIC!!! I'm doing this since they hint at it in multiple episodes of the show.

You and Sam had known each other for the longest time. You had been hunting with Sam and Dean since the beginning. Over the years, a lot happened. More recently being the fact that Sam had just gotten back from Hell.

He had jumped in the cage to save the world. He was a hero. That's how you saw him, at least. You knew Sam was tortured in Hell, but unbeknownst to you, Lucifer did a lot more than just tortured him. He SA'd him, too.

Sam didn't tell you, though. He didn't want you to look at him differently. You were his girlfriend. How was he supposed to tell you another man did that to him? But you knew something was wrong when he'd push off sleeping together and even avoid kissing you.

One day, when you two were in the motel room and Dean was out getting dinner, you started talking suggestively to Sam... which only made him uncomfortable, and you picked up on that...