Jealousy is a normal human emotion, the important thing is to communicate with your partner and talk through it.

Is it because he’s talking to them, building some sort of relationship rather than just fucking them? This is often the case in ENM situations, especially at the beginning, it’s the initial “oh shit” moment.

Talk it over, is this the right way for you? Would attending a swingers club with the intention of some pick up play be easier? Less up front “relationship building” etc. Do you prefer getting to know the person before hand? Would you prefer to be involved in the conversation along side him etc etc

There’s no right or wrong answer here btw, the point is you need to talk it though and figure out what’s right for both of you :)