Welcome to the forums, you've come to a good place.
I'm sure that there must have been some triggers in the last week that you are leaving out as being private, but the only way forward is to figure out what caused the change from acceptance and compersion back to jealousy and aversion. With luck you and your wife have good communication already and are/will be able to discuss this openly. My gut tells me that this may have happened a bit too fast for you, going from one BF to 3... had the two of you discussed what you both wanted out of opening your relationship and the addition of adding more people as she has done?
It is completely possible that you are mono inclined or are just not ready to venture out. You stated here that she has been your "one and only" so there shouldn't really be much surprise that you are hesitent and uncomfortable with "rejoining" the dating scene. Remember, just because she has others, doesn't mean you have to, although I can understand why you thought it might help. My husband isn't sure if he wants/needs to find an "other" if I happen to find one. And that is OK.
But you really do need to start dissecting what triggered the backswing. Taking steps backwards is ok and can be a very useful learning experience. Don't be afraid to talk to her about it. It will be hard, but necessary so she knows where you are and how you are feeling.
Life is about the journey and not the destination,
so what better way to know life
than to wander all the roads and paths set before you.