I know just how that feels...
The one thing I might say to try is to find peace with yourself regardless of how your gf responds. Find something that will allow you to relax, feel good, or let some steam off. For me - swimming, bicycling, or racquetball work wonders. As does listening to some great music, or doing something that I don't have time to do If my bf is not around.
Really this has nothing to do with polyamory - more of a how to reduce anxiety in general.
Have confidence that things will work out for YOU regardless of if it does with someone you are in a relationship with... If you find that peace, relationship anxiety can just melt away.