i haven't spoken to him in 4 months so i need a way without directly approaching him to upset him.
Most Helpful Guy
The best way to make an ex jealous is to work hard on improving yourself and have a very happy and successful life. Seriously.
Attempting any kind of subterfuge or trickery or petty little things to try and get at him will only serve one purpose. Making him 100% sure that he made the right choice in not committing to someone with revenge issues that holds a grudge. That is the type of woman that every guy in the world can agree is one to steer far, far away from. Anything that hints at 'crazy ex' will spread like wildfire and serve as guy-repellent to anyone who has heard the story.