Hi again OP.
Look at it this way. She's the one missing out, not you. Do you really want to be with some one who claims to love you but then sleeps around? Thats not love, thats just playing somebody along.
From the looks of your sig you have a 'bright future ahead of you' (which is more than what i have so be grateful). If you move away to uni you are gonna meet so many new people and you will find somebody out there who will like you back and who wont sleep with other boys.
Dont drown your sorrows. Cos when you wake up sober in the morning your problems are still there waiting for you and it feels like you have to start all over in your head sorting it out.
Breaking up is never easy, its not supposed to be, but if everytime you feel sad or lovely you run back to her, you arent moving forward, you'll just go round and round in circles. Of course you will want to get back with her now, but remember, there was a reason for why you broke up, and it obviously made you unhappy enough to finish the relationship, so no matter how nice your memories of the happy times might be, it obv wasnt a good relationship worth fighting for.
From past experience, i think the hardest thing is breaking up but keeping in touch. Everytime you hear them or see them it just makes it worse, its like breaking up all over again. Its harsh and really hard but the best thing to do is to just cut all contact with her. Eventually you'll get used to not having her around and then you can be happy again.