Long distance relationship--My girlfriend and I think we don't deserve each other. Is that unhealthy?

I first met my girlfriend almost a year ago at a place we both worked at for a summer job. We were together all summer and had an awesome time and were very happy. We arent from the same town and both go to different colleges about 5 hours apart and towards the end of the summer we decided to start dating because we didnt want to end what we had, and we really believed that we could work through the long distance. She is really a great girl- down to earth, kind, trustworthy, beautiful, not crazy- and i honestly have never before met a girl like her, and she thinks the world of me and trusts me. We see each other every 2-3 weeks and it's always been a good time, but i just dont seem to have that spark for her that i had during the summer and fall, and i have no excuse for it- she hasnt changed one bit! Maybe it's the distance, i don't know, but she still thinks the world of me- probably more now than she ever has. She tells me that she doesnt deserve me and that she doesnt want to lose me, but i counter by saying that I dont deserve HER, and i honestly believe it. I hate saying it, but the future looks tough. This summer she's working 900 miles away and then next fall is taking a semester abroad. I sort of feel like we're just infatuated with the IDEA of each other...does that sound right or even exist? What can I do? Thanks.