I need help getting myself out of it

I (19M) have been with my girlfriend (20F) for almost 4 years now. but 2 years ago, i had cheated online during a break that we had, and she chose to stay as long as i made the actions to change. since then, i haven't thought of doing anything to betray her, and have stuck to making sure i do well on that part. but everyday it's like i'm reminded of the choice i made and it kills me. i hate knowing what i did and i hate knowing that its something i would never have done now. and even so, because shes given me another chance to keep the relationship going, i've been kinda just passing everything bad that happens as something i deserve. like when im being berated or yelled at for anything i feel like its exactly what i deserve for what i've done to her. its gotten to the point where i've had times of sh constantly and being ashamed of speaking up or choosing to stand up for certain things. it's not like shes a bad person, shes extremely far from it. but since then everything thats been happening almost feels like the end of the world. i'm almost scared to do anything that might even bother her to make sure i do the right thing. it hasn't helped that I'm also in college + work and struggling on both. i've been wondering if it might be better if i chose to simply give up and leave everything i have to her or family. i just feel lost and i really could use some pointers on what i should even do