You thought that the past was behind you, but then your ex pops up acting like he's still with you. Whether he has a never-ending stream of questions about your new guy, makes jokes at your boyfriend's expense or is just constantly around, knowing if he's jealous of your current relationship can help you deal with the situation.

Notice Nostalgia

When an ex idealizes the past, chances are she is wishing she had you back. While the cause of her picture-perfect view of your relationship may include her own sadness or that her life isn't going as she thinks it should, it may also include jealousy over your new love. Striking up nostalgic conversations about past "awesome times" to the exclusion of the problem periods the two of you shared may signal a pang of jealousy on her part. For example, she may say something like, "Remember how much fun we had going ice skating together?"

Famously Flirting

You're at a party, school dance or other social gathering with your new guy when your ex walks in. He glances over in your direction, then heads for the closest attractive girl. When he knows that he's in your view, he starts dramatically flirting with her. Making sure that you take note of his fiercely flirtatious ways indicates that he may be jealous of your new relationship. Competitive flirting is an indirect way the green-eyed monster can come out, according to psychologist Suzanne Phillips in the Psych Central article, "Understanding Jealousy in Your Relationship."

Jealous Jokes

During a friendly conversation with your ex, she soddenly exclaims, "I saw that outfit your new girlfriend wore to the football game. Wow, I didn't know shorts could get any shorter." Does your ex really care what your new girl wears? Probably not, but she is most likely jealous of your new relationship. Making digs at your new love's expense doesn't indicate that she's suddenly become a mean girl. Instead, it signals her jealousy.

Constant Contact

Your ex didn't text you dozens of times a day when the two of you were together, but now he is over-communicating with you. If he starts checking in on you, wanting to talk all of the time or interrupting your date nights with an ill-timed phone call, you're seeing his jealous side. Even though he knows that you've moved on, his constant contact is a way to re-insert himself into your life and possibly push your new guy out.