my advise is that you un-commit to your girlfriend, but keep in touch. If you can't be around each other without losing control, then agree to stay away from each other awhile. If you really like her, which it sounds like you do, then check on her, call her, but keep a healthy distance for the both of you.
You are so young and have so much life ahead of you. You need more experience in the outside world. If you are a Sr, then your whole life is about to change, most likely (i.e. whether or not you're going to college, friends leaving, getting a job, living on your own, etc). Take a deep breath and just relax. You owe it to yourself. You don't have to decide anything until your ready. Just be careful and always safe. Use a condom always and respect yourself and your girlfriends and girl friends.
Your decision to spend the summer getting the flirty out of your system was a good one. Be honest with each other and remember that you want to be happy. Ultimate goal for everyone. So, take your time, pray like hell and listen. God really does listen. You just have to hear him. So, if it doesn't feel right, don't do it.
Hope this helps.