Need advice on my situation plz?

i found out i am pregnant im 22 the father is my ex. My ex was not a good guy. Everything that came out of his mouth was a lie he used me (lived off of me) treated me and my posessions like crap. He has an anger problem i was always getting freaked out on. It was always like walking on eggshells around him. He screwed with my head so bad. i gave him so many chances after all the times he screwed up because i did love him and i thought he would change. He was cheating on me with a 15 year old in my bed numerous times when i was at work. Theres a lot of bad things he did but it would be a novel by time time i told you all of it. I told him a couple days ago that he is going to be a dad. And now he wants to get back together and said he would change and is already changing and wants to be a family. I want my baby to know his dad and for him to be involved in the babys life and at the same time would like a family. I dont know if i could ever forgive him and trust him again after all the lies hurt and the cheating. All i want to do is protect this child and myself i do not want things to be like they were before when i was with him. I am scared and dont know what to do. Should i let him back into my and unborn childs life? will he change or will it just be a repeat of last time?