If you are shopping for a loan, don't have a lot of mortgage companies pull your credit. Each pull will drop your score. Stay away from on line lenders, like Lending Tree, where they "Compete for your business". Each lender on lending tree will pull your credit, dropping your score several points.
You need to work with a lender, locally, who is willing to help you raise your score, by guiding you through what will improve your score to 640 or better. Do not do it yourself, without guidance, you could make it worse without meaning to lower your score. Lending is always the first place to start when looking for a home. I can recommend lenders who do VA and will help you with your score.