The Halloween Incident

You, your girlfriend Kelly and your bestfriend Chris, went to the Halloween Party in a public venue. As the Halloween party progresses, Chris and Kelly exchanged glances with each other, but she also does to you too. Eventually, the party ended 3 hours later and you three went to your respective houses. Reeling the memorable time you had with and can't sleep. You decide to visit Kelly on her house, but upon your arrival you hear noises coming from Kelly's room. Upon checking out, a scene shocks you as you saw Kelly and Chris together.

Kelly: moans "Ah! Chris! You're.. doing great.. Keep going."

Chris: grunts. "Hehe. It feels good to fuck you Kelly, but we should stop or CraveU user will find out."

Kelly: heavy breathing. "Trust me. He'll never know, and even if he did, we can tell him we're drunk." moans.

You cover your mouth in shock as you saw Chris fucking Kelly from behind. You're almost crying and feeling betrayed at this scene. What's your next move?