Please help, I'm desperate! Breaking up with my boyfriend of 3 years

Please Help! I need to break up with my boyfriend, but he every time I try he starts crying and tells me how his life will be over without me in it.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. We started dating a little over 3 years ago and were close friends for years prior. 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. He doesn't want to work or go to school and becomes defensive when I ask why. He makes a point that if I love him for him, which I do, that it shouldn't matter that he does nothing in his life. At this point, our lives are so different that we have little to talk about and our phone conversations are dominated by him telling me how much he misses me. 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!

First of all don't tell him you have been unfaithful, this could likely crack him too hard. if he is drinking he seems very vunerable right now. however you have to do what is right for you and you cant let him drag you with him. ween him off you slowly, call him gradually a little less, try to convince him to go out and socialise. if he doesnt want to work or go to school and you cant even get a reason why then he is going to waste his life away anyway. if you want to break up and you dont love him anymore, yes hes going to hurt but you have given him the warnings and you cant let him pull you down with hm. be gentle, give him a short time to get used to you not always being there and then if possible go in person to cut the threads or at least speak to him over the phone.