There is already an object named 'Users' in the database. when using dotNetOpenAuth

I'm using this InitializeDatabaseConnection in my global.cs file but I keep getting an error:

There is already an object named 'Users' in the database.

when I try use my DB context

protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();

            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            ControllerBuilder.Current.SetControllerFactory(new NinjectControllerFactory());
            ModelBinders.Binders.Add(typeof (MasterUserSessionModel), new MasterModelBinder());

            AuthConfig.RegisterAuth();
         

            WebSecurity.InitializeDatabaseConnection("db", "Users", "Id", "UserName",
                                                     autoCreateTables: true);
        }

public class DB : DbContext, IDbContext
    {
        public DB()
            : base("db")
        {
            this.Configuration.LazyLoadingEnabled = false;
        }

        public DbSet<User> Users { get; set; }
        public DbSet<Company> Companies { get; set; }
        // public DbSet<User> CustomProfiles { get; set; }
        public DbSet<Investor> Investors { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            modelBuilder.Entity<User>()
                .HasMany(u => u.InvestorsFollowing)
                .WithMany(i => i.FollowingUsers);
            modelBuilder.Entity<User>()
               .HasMany(u => u.CompaniesFollowing)
               .WithMany(i => i.FollowingUsers);

            Database.SetInitializer(new MigrateDatabaseToLatestVersion<DB, Configuration>());
            base.OnModelCreating(modelBuilder);
            //try
            //{
            //    using (var context = new DB())
            //    {
            //        if (!context.Database.Exists())
            //        {
            //            // Create the SimpleMembership database without Entity Framework migration schema
            //            ((IObjectContextAdapter)context).ObjectContext.CreateDatabase();
            //        }
            //    }
            //    WebSecurity.InitializeDatabaseConnection("db", "Users", "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);
            //}
        }

        public IQueryable<T> Find<T>() where T : class
        {
            return this.Set<T>();
        }
        public void Rollback()
        {
            this.ChangeTracker.Entries().ToList().ForEach(x => x.Reload());
        }
    }