How to break up with my best friend

A little over 3 years ago I started dating my best friend. To give you a picture, my boyfriend is a 21 year old male, with shoulder-length hair and a beard, 5'11" and 220 lbs, while I am a 5'7 female with long brown hair, 110 lbs. My boyfriend and I lived together for 2 years. We stopped living together when I graduated from college and moved 6 hours away to continue my education. My boyfriend completed one year of college and has since lived in an apartment that is paid for by his parents on an allowance provided by his parents. I love my boyfriend, but I have never been entirely faithful to him. He does not know this. I really want to move on and love him in the way you love your best friend or your brother. He literally sits around drinking and waiting for me to call him. I don't want to hurt him, but I know it is better for both of us if we find someone more in-line with who we are. Its so hard to hurt the person I love the most, so I don't know how to go about breaking up with him. Any advice would be greatly appreciated!

You need to do it as nicely as possible, but still get the point across. Don't try to put on the "bad guy" uniform to make him look better and make it easier for you by forcing him to hate you. You're already going to be the bad guy (or girl) because you're dumping him. You need to be as straight forward as possible too. No maybe's, if's, or when's. This will help him move on much quicker because he won't cling onto you saying "Maybe in 7 or 8 years when..." You can't give him anything to hope for, not even friendship. At first, you will have to cut all communication with him for a while. This will also help him heal and move on more easily because every time you talk to him, it will remind him of when you two were together. He's going to call you, text you, and facebook you during at least the first couple months. Do not reply because you're risking the chance of hurting him all over again, and you don't want to do that. This is mostly if he is head over heels in love with you and is going to take the break-up very badly. If for some reason, he's more amicable to the break-up and seems okay about it, then that's different territory I have no experience in.