It's called Unexpectec Visitor by oliigleegirl1124
I have been looking for a story it's been driving me crazy.
Puck and Rachel are together. I remember that in the story Puck calls Rachel and Rachel overs hears a girls voice telling him to come back to bed I think she mentions his penis in the line.
Puck confesses to her that Quinn was feeling down and he and her got drunk and they had sex.
Than Santana is comforting Rachel at her house. But to there shock they hear music playing Santana and Rachel rush to the window to see Puck singing to to her. After he sings Santana tells her to get her man she rushes down to him and they kiss and she forgives him.
That's all I remember I hope someone can help me. I have been looking for this fic for a while.