Is this abusive? I'm so confused

I've been with boyfriend 4 years and over the years this has gradually got worse. He seems to snap and change. His temper rises and he lashed out on me for the smallest thing. Like today he said something which I didn't answer straight away so he grabs my arm and shouts in my face ANSWER me when I speak to you. When I me grab he really does. His pupils widern and it's like he switches. He's given me bruises and all sorts. The worse he has done is hit me so hard I actually cried in fear. I keep thinking I need to leave but my heart keeps holding on. I'm really struggling.

Edit- I have told him countless times this isn't acceptable but he doesn't listen to me.