And, you owe it to the girlfriend to be polite and treat her well, and the duty to treat her well comes BEFORE the quest for the explanations of your reactions that use a variety of psychological terms, such as "neurotic" (an old term, not in use anymore), "insecure", "fear-based", and so on and so forth.

You should consider yourself very lucky that she has tolerated your presence so far, because based on your description of the gf, she would have some other choices besides you. She does not seem to be somebody who would be desperate and forlorn without you.

I have noticed Payne advising flowers on another thread, as a way to make up for past wrongs, and I cannot find a better way for you to start making amends for your behavior. If the gf likes flowers, that is. But you cannot really go wrong with flowers...