He protests, way too fast, way too much. Of course he's not jealous, what are you talking about! They just fuck out of convenience, nothing more to it, certainly not a feeling of camaraderie and friendship and closeness that he saw glimpses of in the past but never got close to until they were forced into this arrangement.
It's not like he's worried about losing that now. No way.
"I'm just not interested in getting leered at by your latest conquest."