Admin login wont accept passwords please help

The password and username I use to log-in to the admin page of our website was working fine on Tuesday, then all of a sudden it could not accept the password, or identify the user. The password for our account has been changed numerous times since then in an attempt to rectify this and yet we still cannot access the page. We need to access the admin page as we are in the middle of building a new website. we have tried every variety of our usernames we could think of, and still no results.
What could be causing the error? and how can we fix it so that we can get back to business?