How do i get over my cheating childrens father? any good books for motivation?

Hi everyone, just a couple of weeks ago i found out that my boyfriend had sex with a female in MY home. i was able to get her and him to admit everything and in the end he told me he wants to still be with me but he wants to sleep with other women and that thats what hes going to do no matter what i say. a little info about me im 22 and we met when i was 16 and a virgin. i wasnt close to my family because of certain issues so i moved in with his when i was 17(hes 25 now). i guess we just met to young. he tells me that he loves me and he wants to marry me in a couple of years but right now he wants to be with me and a whole bunch of other women. everyone has been telling him that hes wrong but he just doesnt care...what kills me is that i consider his family as my own and now i feel like i have lost everything n everyone....we have a 3 yr old son and im about 5 months pregnant with twin boys. i guess we just met to young and hes an a**... i know i cant get him to stop cheating so i need a way to get over him. i would like to hear what you have to say and if you know about any books that will motivate me to be strong at this time i would appreciate it. thank you