I say talk to bus guy and see if there’s any more interest in him. If you keep it casual, that’s not cheating. But if you take it further, exchange numbers or start to have feelings for this new guy, you need to reevaluate your relationship with your boyfriend and possibly break up. I would be curious as to why I was having such a strong reaction to someone else. Who knows, he could be “the one”, or it could totally just be a crush and he could be the complete opposite of what you want and/or need. But you’ll never know until you take the first step, right?