I am also 5'7" with a 28" inseam and I have a 17" frame on both of my bikes. I am surprised that you didn't have more attention to what size would be the best fit for you at the LBS. I'm sorry but I feel that no matter how busy a shop is they should spend the time with you for a propper fit. I've read a hundred posts here and on other boards where people are saying "don't buy new bikes on line, you need to be professionally fit and serviced so buy your bikes from a LBS." I feel your bike is too small for you and I don't blame you, I blame the people that sold it to you.