I had fleas get in my house from an ex-roomates dogs about 1.5 months ago. I’ve since used every method, spray, powder, and foggers, but they keep coming back. I’ve even sprayed my back yard with flea killer every couple of weeks. There are a couple stray cats that come around my neighborhood. Could it be that they have fleas and are depositing them in my yard and having me track them in? I am really lost here.