Why do you have to all sleep in one bed? If it's because your'e having threesomes, stop having them maybe? I don't really understand being jealous if that is happening. If you're not having them, no reason to share a bed at all?
Really, go sleep at her place, or don't have overnights in a shared bed (and if you share a place with your fiance, HE isn't the one who should be kicked out of bed). I sure wouldn't let non partners be interrupting my quiet rest time. That must be uncomfortable for her too.
Happiness will never come to those who fail to appreciate what they already have.