From observing others rather than a direct experience:

jealousy that comes from a past relationship is very unflattering, unsexy, unappealing, and unarousing. This is because it has nothing to do with the current object. It is not about your desire for the current girlfriend and your thinking that all the other men within her earshot desire her as much as you do - the flattering part.

It is rather about your imputing to the current girlfriend things from your part girlfriends. Not sexy. Not passionate. Not flattering. Not even about her. So drop that if you can.