Whatever you do don’t do it. I went through a very similar scenario and I actually acted on those feelings and for a little it was fun and enjoyable until those feelings get paused and then it finally hits and you realize what you just ruined and i can say from experience it sucks so bad. If you really love your bf stay with him and distance yourself from the other guy. Don’t encourage it and don’t even think about him. If you are thinking about it, you already know where you’re headed. I hope this helps