If you are the jealous type, then you ARE the jealous type and there is nothing, but nothing that you can do about it. There are varying degrees of jealousy and of the most serious type, goes anguish, pain and mood changes which makes life difficult.
We ALL have a degree of jealousy and for some it is a sexual "turn on" to see their partner.."chatted up" but for others, it has the opposite effect.
Situation that you describe is that of a failing relationship....but who knows, human behavior and emotions are complex issues.
What should you do? NOTHING, just wait for a relation changing event, which may or may not arrive.
Jealousy comes with an inferiority complex mixed with an anxiety state.