This happens a lot in life, you shouldn't have let it get to this point but since it has. You need to take a step back and reevaluate your relationship with your current girlfriend.
11+ years is something to be proud of, it takes a lot of hard work to get where you are now.
You need to ask yourself how much your girlfriend means to you and as well as how much she loves you. To be honest being with a girl that long I hope you do love her and if you don't than you're fucked up.
If I were you I would be a man and just talk to your girlfriend and communicate about your life together as of now. Who knows...maybe you will change your mind and make things work. Because I do feel sorry for the girl right now.