Dream cheating

So last night I had a vivid dream my fiancé cheated on me and I woke up so unbelievably upset. It's happened before so when I tell me fiancé he always apologizes for what he did in my dreams and tells me he loves me. He is seriously the greatest man ever even when I'm being irrational! I'm just curious what others have experienced with this! It doesn't happen often but when it does I'm pretty shaken by it!