Life goes on

How do i tell my bf of three years that I’m not in love with him anymore. I haven’t found interest in someone else or just lost feelings for him. It’s just that i realized how different we grew apart and how the beginning of our relationship was amazing but as soon as he got comfortable he became rude, cold hearted, selfish. He never appreciates my kind gestures and he’s always speaking to me in a stern voice. He was never like this, i don’t know if he hid this part of him. I’ve spoken to him so many times about how rude he is when he speaks to me but i don’t think he cares. I have no other choice but to tell him I’m not in love with him so he can break up and move on. I deserve to be treated better.