Shopping around for a mortgage

[Adam Juodis]

I received pre-approval last weekend, but I would like to shop around and see what other lenders have to offer me. What I am trying to prevent happening is my credit score being pulled multiple times, and the pulls actually adding up against me.

If I ask a few more lenders for mortgages, will the credit bureaus combine the hardpulls? Is there a certain time limit between the inquiries or amount of times that is the so called 'grace period?' Also, should I let the potential lender know that I have been shopping around- does this work to get a more competitive rate? Thank you!