Turn off the "Include IF NOT EXISTS" option.
It's at Tools..Options, then click "Scripting" on the explorer pane of the dialog that pops-up. the "IF NOT EXISTS" option is in the second group from the top (Object Scripting options).
EXEC dbo.sp_executesql @statement = N'-- =============================================
-- Author: Me
-- =============================================
CREATE PROCEDURE [dbo].[MyProc]
-- Add the parameters for the stored procedure here
@StartDate datetime
AS
BEGIN


