model changed, update database using codefirst

Im using code-first to create a database. And now im trying to make a linq expression to get data out of the database but then i get this error:

"The model backing the 'FantasySport' context has changed since the database was created. Consider using Code First Migrations to update the database"

So i go to package-manager console and types update-database and it says that there is nothing to update.

"PM> update-database Specify the '-Verbose' flag to view the SQL statements being applied to the target database. No pending code-based migrations. Running Seed method."

----EDIT------

Here is the initializer method:

  private class SimpleMembershipInitializer
    {
        public SimpleMembershipInitializer()
        {
            Database.SetInitializer<UsersContext>(null);

            try
            {
                using (var context = new UsersContext())
                {
                    if (!context.Database.Exists())
                    {
                        // Create the SimpleMembership database without Entity Framework migration schema
                        ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
                    }
                }

                WebSecurity.InitializeDatabaseConnection("DefaultConnection", "UserProfile", "UserId", "UserName", autoCreateTables: true);
            }
            catch (Exception ex)
            {
                throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized. For more information, please see http://go.microsoft.com/fwlink/?LinkId=256588", ex);
            }
        }

So what is the problem?