Multiple controller constructors when injecting dependencies using Unity.Mvc5

I'm very new to dependency injection and I've just set up Unity.Mvc5 and has some success with it. But now I face the problem of multiple contructors in my controller class. I already have constructors that handle my UserManager and following tutorials I understand I need another constructor to instantiate my interface. When I do this however, I get the following error:

The type OrganisationController has multiple constructors of length 1. Unable to disambiguate.

A snippet from my controller:

    private IPush _pushMessage;

    // Here is the problem!
    public OrganisationController(IPush pushMessage)
    {
        _pushMessage = pushMessage;
    }

    public OrganisationController()
        : this(new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext())))
    {
    }

    public OrganisationController(UserManager<ApplicationUser> userManager)
    {
        UserManager = userManager;
        var provider = new DpapiDataProtectionProvider("MyApp");
        UserManager.UserTokenProvider = new DataProtectorTokenProvider<ApplicationUser>(provider.Create("PasswordReset"));
    }

    public UserManager<ApplicationUser> UserManager { get; private set; }

And my UnityConfig.cs as follows:

public static class UnityConfig
{
    public static void RegisterComponents()
    {
        var container = new UnityContainer();

        container.RegisterType<IPush, PushMessage>();
        container.RegisterType<IController, OrganisationController>();
        container.RegisterType<IUserStore<ApplicationUser>, UserStore<ApplicationUser>>();
        container.RegisterType<DbContext, ApplicationDbContext>(new HierarchicalLifetimeManager());

        DependencyResolver.SetResolver(new UnityDependencyResolver(container));
    }
}

I am not sure how to tell Unity that I have another constructor being used to implement an interface.