stored procedure of contact us table in asp.net does not execute correctly

ALTER PROC SP_Contact_Msg
--@Reg_id as int, 
@Email as varchar(50), 
@txtName as varchar(50),
@txtBody as varchar(50) 
AS
BEGIN

    DECLARE @Reg_Id AS INT

    SET @Reg_Id = (SELECT TOP 1 Reg_Id FROM reg WHERE Email = @Email)

    IF @Reg_id != NULL 
    BEGIN 
        INSERT INTO Contact ( Reg_id, Email, txtName, txtBody, CreatedOn, CreatedBy, UpdatedBy, UpdatedOn, IsActive) 
        values (@Reg_id, @Email, @txtName, @txtBody, GETDATE(), 1, NULL, NULL, 1) 
    END

    IF @Reg_id = NULL  
    BEGIN 
        INSERT INTO Contact (Reg_id, Email, txtName, txtBody, CreatedOn, CreatedBy, UpdatedBy, UpdatedOn, IsActive) 
        VALUES (null, @Email, @txtName, @txtBody, GETDATE(), 1, NULL, NULL, 1) 
    END
END

please help me this procedure does not work correctly when i give email of register(reg) user email its not show the (reg_id) just show null, its only execute only else condition