Sex before marriage

I was sorta forces into Christianity by my mom until I finally gave in. I now do believe in God and I do love everything about it. Although I do have sex... I feel guilty every time after it. I want to tell my partner I really don't want to do it anymore. Just to wait until marriage and for real this time. I don't know how to tell him. I've brought it before and he just says he doesn't mind because he doesn't really care about it. But he thinks I won't stick to it. Then I think about it and say well I've done it already. Will there really be a difference in stopping? I don't know what to do..