It’s possible, but it could also backfire and make him think you’ve moved on.  If you really feel the need to date, then do so if you need that to be happy.  

But if you’re considering going out with someone just to make your ex jealous, that’s not really fair to your date, or you.  Games like this usually don’t work.  Be honest with yourself and others, and you stand a better chance of getting back together with your ex.

No matter what kind of deception you’re thinking of, even if it doesn’t seem harmful—forget it now.  Even the most innocent-seeming lie or exaggeration could backfire later.  What’s the point of figuring out how to get him back only to lose him a little while later because he finds out about your dishonesty?

This is probably the hardest situation to overcome. Not only is it difficult to be alone with him if he has someone else, he’s focused on the new relationship.  You’re part of the past, and not a priority.  Being nice right now is crucial.  You have to make him see how wonderful you are and how much he’s missing.