I have been in a serious relationship for about 3 years. As I am going back to grad school we wanted to hold off marriage until I finished and just date exclusively until them (another 4 years). A few weeks ago we got in a huge fight. I am a really easy going, funny and carefree guy and she thinks I am too childish and we broke it off. Looking back at the three years, I have changed a lot I am more mature and serious now. Not dating her made me realize that the things I was doing were actually really childish, I am totally committed and serious about taking our relationship to a new level. We have hung out a few times since then, I have told her how I feel and that I would marry her and try to get into a instate school. On one of our dates we even went to "look" at engagement rings. She says she has an awesome time with me and loves going on dates with me, but she also says that she wants to date other guys and see what's out there.
My take on this is that:-
1. she is just dating me until she finds someone better
2. she will date a few guys and have to settle for me.
3. I also told her that dating 2 or 3 guys might not help as there are so many guys out there, so what am I suppose to do wait for years?

Any ideas on how I should handle this? I do not want to date other girls and I am totally serious about her. Thank you for you advice and sorry for a long question.

She just may never be happy if she is always wondering what it would have been like with somebody else so you have to let her go and if she comes back you know she must be happy with you. If she doesn't then not much you can do.
What you should do is if you happen to meet someone you wouldn't mind going out with remember you are just as free as she is and you don't want to limit yourself to waiting when you have no guarantee that she will come back.

Uh I don't think so, don't go out of your way anymore to try to keep this relationship alive when she clearly wants to date others, nothing you are doing is good enough, you went out looking for rings, you even want to go to an instate college, your doing all this for her, which you shouldn't it should be FOR YOU.. There is a saying what you sacrifice to keep you may end up losing.. Besideds after she dated these other men, I don't think you will look at her the same... If you don't want to date others, you can't hold that against her because that is your decision... however you can't control what she wants and that is to date other people, finish your school, do what you need to do to become the better you... and don't be responsible and take blame for being childish, she stayed with you 3 years before she communicated this to you, and 3 years ago you weren't the same of course you wouldn't be you get older, your priorities and responsibilities change, but since she wants to go backwards and feel she is missing out.. let her go.. she may regret her decision she may not... either way DO what's BEST FOR YOU...

Your 3 scenarios are correct, and whether you agree or not, she will date others. Knowing that's what she wants, let her do what she wants, and you can continue your own life, and do as you please, without her. It happens in life, the unexpected changes our plans, and we get thrown for a loop for a while, but we cope by accepting things for what they are, and regrouping with a better plan. Part of life.

Thank you people. Your insight has been really helpful. I am going to see her this weekend, and I'll say that hey I am serious, and I think we can have a great life together. We should date exclusively and move towards getting engaged/marriage. If she is not ready for this then I'll have to break it off and move forward without her. Thanks again.

Word of warning, don't give it to her as an ultimatum, especially if you can't follow through with it. In this situation, I actually wouldn't ever give her the "or else" choices. I would just break it off and let her live with her decision. If she isn't happy with it than she can decide on her own to be with you exclusively. (You should think hard about whether you want to be with a girl that does this to you) Otherwise, she doesn't get you at all. If you do this it will give you the power over the situation and keep her from controlling you and stringing you along.