If your boyfriend has done nothing wrong, just stay with the man. There is a huge difference between love and lust; and it seems you're getting mixed up with them by thinking you 'like' this friend of his. When you love somebody, you get attached to the personality they have; not the physical attraction which is associated with lust.
Well if you like your bfs friend "a lot" then why are you still with your bf? I think you should talk to your bf about it and then talk to your bfs friend to see if he likes you the same way, but think about it, do you really love your bf? Or his friend? Good luck and make the right choice :) hope this helps