That loving feeling is gone for my girlfriend of 2 years. What should I do?

It sounds to me like you are a fairly Intelligent guy and more than likely you have experienced this before without acknowledging it. I think you are just getting bored.. You all but said it. You need to talk to her once you get back and let her know your feelings. If you want the relationship to continue you need to be honest and bring something new to the game yourself. If she loves you she will be able to compromise and put some spark back in the fire. If you do talk to her and figure out that you don't want to continue then cut it off before you go any further.. That way both you and her can get on with your life.