Of course, your feeling can change. There might be a day where you stop loving the other person. But, the thing that matters is if you actually act on it or just keep it to yourself? There are reasons why people cheat. It's your choice to ignore those feelings, or actually act on it. If you are unhappy, leave. If you still love the other person, just don't do it. But again, this world has never been just black and white right? It's a complicated world. Your choice doesn't only affect you, it affects others too. Like a ripple effect.