What's wrong with ME

I'm not sure if I stupid or idk. I've taken back my kids dad time and time again. And no matter how many times he promises he's changed or I get pregnant how things are gonna be different they never are. As far as my standards or what I'm expecting. And god forbid if I tell him what he's doing wrong or what I expect I'm always the bitch or he has to much on his plate. After our second child he lost his dad. And just gave up on everything. Until I agreed that we needed to end things and started hanging out with another man. He came to my home with a gun shot if off and went to jail. And the year he was gone he begged and pleased how that wasn't him, he made a mistake, he did it out of love, he wants his family back for a year and once again I believed him. But here we are pregnant with my third child by him and he hasn't changed in the way I need him to or what he made out he'd be. I dont want to ever try for a relationship again. I'm over trying for the one I have. I'm working 40hrs a week pregnant still coming home being a mother and tending to my two children. And he's over here not doing what he needs to stay out of jail or to be a person me or my children need like wtf. I'm not the easiest person to be with but I cant he the worst. I use to pack his lunch was his clothes do everything for him until he never was home or acting like a family man. Ugh really just need book on what I'm to do in this life what I'm here for. I'm gonna be alone for the rest of my life I have 3 kids live pay check to pay check and never no matter how hard I try seem to be getting anywhere with anyone. And who's gonna want a single mom with 3 kids who needs help to live day to day. Some days I can understand why I'm never included in family events. I'm the black sheep I dont get why I'm here. Am I hurting my kids by them seeing me like this. I wanted my kids to have everything i never did and all i did was but myself in the same situation i remember as a kid. Single mom who worked her self to death and was mistreated by men. And now is still alone to this day. When will The cycle has to end. I pray with me I'll never love again but my children.