A friend walked in on me and I had to cheat to keep it a secret from my boyfriend

I was in the middle of a steamy session with my friend when all of a sudden, my boyfriend walked in. My heart was racing, and I knew I had to act fast. I quickly covered up, pretending like nothing was wrong. But the look in his eyes told me he knew. I had to come up with a plan to keep him from finding out the truth. I told him a wild lie, saying that my friend and I were just practicing our acting skills. He bought it, and I breathed a sigh of relief. But the guilt was eating me alive. I couldn't shake the feeling that one day, the truth would come out. And when it did, it would destroy everything.