i know i need to break up with my bf but It feels so hard

My boyfriend and I have been together for about 3 years now (we work at the same place) and we're toxic and fight almost everyday. He's cheated 2 times (most recently was when i found out in September but idk how long it was for before i found out) yet I stayed because of the comfort and familiarity i find in him. I genuinely love him but i'm so tired of fighting and most of the time I start it but it's because he doesnt things that I don't like and have told him multiple times. And i'm sure most of it also stems from him cheating and it is always in the back of my head. And the most recent time he didnt even apologize or block her until a month later when i had to take his phone and do it myself. And i've known for a long time we need to break up but we also fight, he says hes done, i say ok, and then the next day or two we are fine and acting normal. I know I need to put my foot down and say no we are done but its so hard. But i'm young (21) and i know theres so much more for life to offer but sometimes i cant imagine being without him but sometimes i just want to be done with it. When i have him im happy but i also know i should let ie end but when it does end all i want is him. Its been this cycle for so long and im so exhausted. And sometimes i feel bad for leaving but then i'm like ?? He cheated twice didnt even apologize the second time??