Retroactive jealousy: when the doubt is about their past
Their history is not a threat to the present, and yet you cannot stop searching it. The compulsions are the same as any jealousy, and the answers help for an hour.
Nothing is happening now. You trust them, mostly, about the present. What you cannot leave alone is before you: who they were with, what they did, how it compared. You ask for details, and the details do not help; they become images, and the images become the thing you replay. You search for the person, look at old photographs, imagine scenes you were never in. And you know it is absurd, because it happened before you existed to them, and the knowing does not touch it.
This is sometimes called retroactive jealousy. It is treated the same way as jealousy about the present, because underneath it is the same machinery.
What is happening
The doubt in retroactive jealousy is not really "did something happen?" You know it did; it is the past, and they have usually told you. The doubt is about meaning. Did it mean more than what we have. Am I less than that person. Would they rather be there. And because those questions cannot be answered with facts, no quantity of detail settles them. Each answer produces a new image, and each image produces a new question.
This is the structure of OCD. An intrusive thought, unbearable uncertainty, and compulsions that relieve it for an hour and strengthen it permanently. The compulsions here are questioning, imagining, searching for details, comparing, and the mental reviewing that runs for hours without anyone seeing it.
Why details make it worse
People with retroactive jealousy often believe that if they just knew everything, they could finally put it down. So they ask for more. Names, dates, what it was like. And every detail becomes material. A vague sense of a past becomes a vivid scene, replayed with the precision of a memory that is not even yours. The search for the last detail that will settle it is the thing that keeps it unsettled.
There is nothing to find that would end this, because what the doubt wants is not information but certainty about meaning, and that does not exist.
The comparison underneath
Very often the engine is a belief about your own worth. That you are being compared and found wanting. That the past was better and you are the compromise. That if they could have that, they would. These beliefs are usually old, older than the relationship, and the jealousy has attached itself to the most available evidence for them. Part of the work is finding the belief and looking at where it came from, because the jealousy is often the belief's latest project rather than its cause.
Stopping the search
In the CBT work, the compulsions get retired gradually and by agreement. Not asking the next question. Not opening the photograph. Letting the image arrive without following it into the scene. Not comparing. The doubt rises, and then, given nothing to feed on, it falls, and you find that you can get through the evening without the answer.
Alongside that we work on the beliefs about worth and abandonment that are usually driving it. Where an earlier betrayal or abandonment is part of your own history, EMDR can take the charge out of the memory that keeps proving the belief.
What I will not do
I will not tell you their past does not matter to them, or that you are better than the person before. Both would be reassurance, and reassurance is the compulsion in another form, wearing off by morning. What I can help with is stopping the need for certainty in order to be in the relationship you actually have.
If you have been searching a past you were never part of, there is more on how I treat pathological jealousy, and retroactive jealousy sits squarely within it.