There are a lot of things I wish to say to you. However, I will keep it brief.
I really wish you could look past your own selfishness and open up your eyes to the pain you’re causing. You break her heart and just when she’s starting to get her life together you go and string her along for another ride.
I know you’re both young and figuring things out, but enough is enough. How many times are you going to do this to someone before you realize it’s emotional abuse? Obviously, you’re the one in control here. And you know it. She continues to hang on and grasp at a future with you because it's HARD letting someone you love go. As soon as she starts to move on you pull her back and fill her with empty promises. Her heart is not a toy! You need to look at yourself and correct this behavior right now.
Regardless of who you’re with -or who you’re not with- you have to be respectful of the other person. If you’re letting them go, actually let them go. It's not right to play with someone's emotions over and over. It's not fair to me to watch this toxic relationship, either. If you regret your decision then maybe you'll think about what you're doing instead of acting rashly.
I'm not your mother, but here is my PSA: The decisions you're making now will affect you for the rest of your life. The way you are learning to behave now are characteristics that will be harder to change the more you grow into adulthood. Stop making the same decisions that have the same results and start learning from your mistakes.