Thank you for the additional information. It helps.
It sounds like the two of you have brought in your own personal issues into the relationship. This creates a crossing of boundaries since your issues then become part of the relationship and become the other person's problem. They also prevent the formation of healthy behaviors between the two of you so you continually hurt each other and have to break up instead of coming together to form a stronger bond.
What you both need to do is identify your own issues and take responsibility for them so you can resolve them. That is the best way to repair the relationship so you can come together in a healthier way.
Your girlfriend's issue seems to be a fear of abandonment. This creates a boundary issue for you since you then become the object of her fear. In order to cope with how she feels and be able to approach your relationship in a healthy way, your girlfriend needs to take responsibility for resolving this problem. The best way to do this is through individual therapy and self help. To find a therapist that can help her, she can contact her doctor for referral. Or she can search on line at http://therapists.psychologytoday.com/rms/.
She can also learn more about abandonment through self help. Here are some resources to help her:
Changing Course: Healing from Loss, Abandonment and Fear by Claudia Black
Thank You For Loving Me!: The Psychology Of Abandonment, Healing, And Loving by J. Ray Rice
As for your own issues, you may want to take a look at your fear of not being loved, anger issues and jealousy. All of these issues can be addressed either through therapy (the best option) and self help. Here are some resources to help you:
It is very obvious that the two of you love each other. And the motivation to repair your relationship is there. As long as you both care about one another and want to be together, you will be able to repair what is wrong and stay together.
I hope this has helped you,