How to break up with my boyfriend of 3 years?

Right now I'm feeling that we're not as compatible as we used to be. We argue too much and I can't do it anymore. I'm really unhappy in our relationship and feel like we're better friends than actually together. We don't do anything lovey dovey anymore. He has different interests to me. I feel bad for feeling this way and know it cannot go on anymore. Has anyone got any nice advice?