Ready for an open relationship?

Please pardon my English. I have being trying my best to keep my relationship working for the last 6 years. I have been cheated on so many times with real people and cybernetic by the father of my daughter. I truly loved him! This is a man that has everything on me. I'm 5'4,120lb, medium dark skin, dark hair, must of the people considers me good looking, Cuban, plenty of , and fun, and above all the mother of his only child. Up to this point i feel jealous of his actions and i wish to start something on my end as well. I think i will like to remind next to him MAINLY because i m terrify of our daughter having parents in different places.( my father left me when i was young and yes I'm scare of her going trough the same). Once i proposed to him about having an open relationship. He refused, stating "that is unfair to you, i will change" At this point is not longer unfair? his behavior keeps going. I think it would be easier for me (i have never cheated or lied to him) if i could have my own "relationships "while he keeps cheating .Can this work? would this be more fair to my self ? Please help. THX