And I say "hopefully" you will lose him because what you have described is a heavy indicator that this is going down a bad path for both of you. You, because you are not in a mentally stable enough position to marry someone if you let yourself put your own needs so selfishly in front of the person you think you love. And him, because he is in for a world of hurt, from finding out that the woman he loves betrayed him, numerous times in a calculated way, that she likely will not take herself out of the environment where her fling is (speaks volumes to your priorities and lack of commitment to work at saving the relationship and make your BF feel safe), and the years he will be tormented by this potentially happening again before you discover why you chose to repeatedly sacrifice your relationship. Even if he does try to forgive you, regaining that trust will quite literally take years and years, and that's no way for either of you to be spending your first years as a married couple instead of being lost in love with each other.
see the review