A: Follow your heart and your don't 2nd guess I love you and everything happens for a reason. At the end everything is great and it if it's not then it's not the end.
A: Take it slow. He might not be ready to hear that you like him because he has a girlfriend. Just give it time. If your going to tell him then you should break it down to him slowly. You might scare him off and I know you don't want that to happen. See how things go because a friendship is way more... more