Most Helpful Girl
You should talk to her about this, exactly this. And if you guys decide it's not going to work out, then that's going to be it. My boyfriend and I live 5 hours apart, we have our own lifes, own friends and aren't together all the time. You should explain her you need some alone time too and that when you are with other girls that doesn't mean you are cheating. I think she is afraid to lose you because in highschool you were together all the time and now you are not and that explains this behaviour you hate. Tell her she won't lose you, because you do love her and i think you should try to work things out. I think that if you talk to her in that way, her behaviour will drastically change. You need to have good faith else it's doomed from the beginning. You love her, keep that in mind and if you have so many things that got you guys back together after breaking up 5 times, i think that is also a sign you just need a good talk. I don't think it is worth breaking up over, because you might never find someone like her again.
Most Helpful Guy
Just don't be that one guy, who breaks their heart and ends up realizing that you want her back. Just talk to her about things bro.