This happens a lot. But relationship has to be about a mutual feeling aydl? I think you just agreed to be in relation with him because you didn't want to lose him as a friend. If you aren't comfortable being in the relationship you should be honest about your feeling and discuss it with him before it deteriorates what you both have. Demo every best friendship doesn't have to be changed to relationship. Respect the feelings he has for you but you need to be honest with yourself and him as well. Discuss it together and decided on what is in your both interest.