You don't have skills to keep your relationship going. You reek with insecurity. It won't last long unless you change.
You are a beta male at this point in your life. You don't know what to do, you're not a leader. Your relationship will last until she finds a guy that can lead. She'll trade a sissy that don't know what to do for a guy that is confident and knows what he's doing, without giving much thought to it.
The best advice you can possibly get is: DO NOT CONCENTRATE ON YOUR GIRLFRIEND.
Look what you doing, she means soooo much to you, that here you are, trying to learn a thing or two, so that you can KEEP her forever. That is wrong.
You can't keep a person with you forever, that's hostage taking. If she wants you, she'll stay with you, by her own will. Understand?
Instead of concetrating on keeping her as your hostage, concentrate on becoming a better man. Go ahead, and ask us, how to become a better men.
I won't tell you until you ask.
P.S. The advice you get from us, is useless to you, because being Don Juan is in your head. You can't fake by doing things or applying techniques, no such thing. Everything we tell you is to transform YOU.