Credit is on the edge? What do i do?

[Samuel Maclean]

So I am have been pre approved at this point for a loan and have been told my credit score is 649.  Some of the loans I qualifty for have a cut-off of 640.  I wanted to look at other lenders but now am worried it will knock my credit score down again.  How much does it knock your credit down each time to get pre-approved? Any advice to a newbie?

thanks