Im getting married in may. We've been together for almost 6 yrs living together for 5.5yrs. Ive had those same bouts of doubt all through our relationship and they get stronger as the months close in. In my heart i know i want to be with this man for the rest of my life. Change is difficult for me although the only real change will be my last name. Like others have said thats not a deal breaker. Im sure you as will I will walk down the aisle smiling and happy and just a bit nervous. Enjoy the day. Therapy might be something to look into if you havent already. Best of luck and congratulations.