So I have to start over again or not?
Nah. It ain't real life, so you don't have to suffer through living again, unless you fucked up bad enough to the point starting new playthrough might be simply faster.
Wait, how do you even start new life playthrough?
Anyway, all you have to do is
to follow that damn train CJ stop dating all girls and butter them up. Increase thier love and trust up to the maximum by other means than dates and actions you could consider affectionate. Basically just complement until filled. After that ask them to follow you, take them all to the pool and repeat it 69 times until they become friends so best willing to share thier favourite mutant dick. Then you just ask about sharing. You do dates
ONLY IF NEEDED to progress thier relationship quests to unlock thier love and trust capacity while taking shit from the other girls, as they are just getting angry at you and will be avoiding you for some time.
But it's just matter of time you are willing to spent trying to fix your mistake. As I wrote, it may be faster to just simply start new playthrough.
Also, no game is bug free and you may even encounter a bug without knowing about it, but realize it was a bug later in your playthrough. Like, for example, getting shit from your friend Jean about dating other girls, because she's not okay with that.