Think about that guy is ok gei, I am sure many married wives or husbands do think abt other girls (like movie stars). I guess my C6 sometimes think of the TV star Suki and Chan Fart Lai ga, haha
However, don't take any action la, you are married ga ma. If you still love your C6, don't do anything to hurt him.
I am married and a few guys chased me (one is super handsome, hehe!) 1-2 years ago. I never thought abt other guys because my C6 is the best C6 in the world, haha!
You always need to keep in mind that your C6 is the best (since you said he's a good guy). You will regret if you choose another guy. You cannot guarantee the new guy will make you happier and give you a better life.
Maybe you should do something more interesting with your C6, so that you can forget that guy. E.g. make a BB, go outings