I need to breakup with my bf, he’s abusive tho

Ive been with this man for a year & a half. There were so many red flags but i ignored them all hoping things would go back to normal between us. We have so much fights, and when i confront him he says that never happened. Which makes me feel like i am crazy even tho im not (ok maybe a little bit). But i dont fancy him any more. Every fight makes me like him less. I feel as if im cheating on him, just by not sharing feelings back with him. He is going to be heart broken but he also screams and yells at me alot. He was my rock & everything i needed at 1 point. Now i feel like he is just holding me back. I am unhappy with him. How should i break up with him?