Lenders will generally pull your credit at least twice -- when you originally apply and shortly before closing (as happened in my situation). If there are any significant differences between the two, such as a new account or a significantly higher debt balance, it could lead to delays and could even disqualify you for the mortgage. Be safe -- just leave your credit alone until you've signed your closing documents.
If you’re behind on your mortgage, or having a hard time making payments, we want to get you in touch with a HUD-approved housing counselor—they’ve been sponsored by the U.S. Department of Housing and Urban Development. Your counselor can develop a tailored plan of action for your situation and help you work with your mortgage company. They’re experienced in all of the available programs and a variety of financial situations. They can help you organize your finances, understand your mortgage options, and find a solution that works for you.