It doesn't sound like you are ready for marriage, but that you are going to have to get married soon regardless. On the other hand, if you are questioning whether she is good enough for you than maybe she is not the right choice for you. How unfair to question that and yet still marry her. Maybe she's a wonderful woman, but not what you want in a wife. I hope you work things out.
Marriage IS for life.
I think you should really take some time to think things over. Give yourself some time. I should hope your family would respect you enough to care that you are happy. And things like money and looks are not the things that will make you happy. Maybe for awhile, but not for long.