The job of the realtor is to help in choosing and purchasing a home. It's fine for them to show you houses until they're blue in the face, but if you can't actually purchase it then he/she is out alot of time and doesn't get paid.
I'm beginning to wonder if the agent is blowing you off because he doesn't believe you are serious buyers.
As MANY of us on this thread have said,
get a preapproval. That does NOT mean you have to use that bank for the loan. It simply is a piece of paper that one lender has written on saying that they've looked at your credit and income and they believe they would write a loan for you up to X amount. It doesn't even hold them to anything hard and fast, as something could come up and they could change their minds. But it does hold some weight in that they're just not given out blindly.
Then with the preap letter in hand, start looking. And in the meantime, call around to lenders, get their rates and fees, and start deciding on who you want to go with. When you find your dream house, make an offer, make a final decision on a lender and then move forward.