The big boys are right dm, more info needed, but what you could try is disconnecting the 2 furthest contacts, and make sure the first one works; if it does, then I suspect you've wired the subsequent ones wrongly. Add the 2nd one, then when you've got the right idea, add the last one.
But having said all that, why have you added 3 door contacts on one zone, how would you know which one was set off (apart from the obvious fact that it might be left open) but unless the doors are being left unlocked, wouldn't vibrations sensors be a better idea. Has this idea been thought through properly.
Mike T, January 2012