My wife became a sub to someone else before we met and still sees him for sessions. I agreed to this but now I'm struggling with jealousy even though I said yes. What do I do?

The gap between intellectually agreeing to something and emotionally experiencing it is one of the most commonly discussed dynamics in polyamory and kink communities. You agreed based on what you anticipated you would feel. The feelings you are actually having may be different from that anticipation, and that is a legitimate development, not a breach of your original agreement.

Some jealousy in this situation is extremely common and does not necessarily mean the arrangement is wrong. Jealousy is typically a response to perceived threat, and understanding what the threat feels like specifically is usually more useful than trying to eliminate the feeling wholesale. Is it a fear that his connection with her is deeper than yours? A sense of being compared? Feeling excluded from part of her life? The specific content of the jealousy tends to point toward what would actually help.

An honest conversation with your wife about how you are actually feeling, rather than how you agreed to feel, is the necessary next step. This conversation is not an announcement that the arrangement must end; it is an honest disclosure that you are having more difficulty than expected and that you need to talk about it.

That conversation might lead to adjustments: more reassurance, more visibility into the nature of the other relationship, a change in how sessions are structured, or a renegotiation of the terms. It might also lead to a clearer picture of what is driving the jealousy that makes it more manageable.

Holding feelings back because you technically agreed to something is a reliable path to resentment.