What do you do when you have a crush on a guy and you think he has a crush on you but he has a girlfriend?

Crushes are harmless, even if he is taken. If he is available, make a move. If not, be friends.

Answerif by crush you mean possibly love then...

if you are siding with the devil on your shoulder, try and break them up and then comfort him until he falls in love with youif you are siding with angel then you just let it be and hope for the best for you. but if you are just crushing i wouldn't worry about it as it will fade very soon. but if it does turn to love, befriend him as well as you can and then when they break up (which if he just has a crush on her then it will fade and they WILL break up) then you can be the one to comfort him because by then, you friendship will be so strong he will come to you for help and see that you care for him which in turn can mean something close to love.