Both parties suffer when a relationship ends, but often one person takes it the hardest. The signs of a jealous ex-significant other are plentiful. They can manifest as both love and hate. If you experience any of these, you may want to tread lightly on his or her heart, because jealousy can only mean one thing -- there are still lingering feelings.
Does your ex-girlfriend still call to talk about old times? Does she sit or stand inappropriately close while visiting? Flirting is a sign that she is having a hard time moving on. She will joke about the shortcomings of your new girlfriend or even friends. Your ex is trying to establish her place back at the top of your chain.
Your ex might also call just to put you down. He will "playfully" poke fun at anything new you are doing. If you broke up with him, he might feel the need to re-assert his dominance. He might also talk about his new girlfriend in an attempt to deflect his jealousy onto you.
Stalking can be as scary as it sounds, or it can be rather passive. Joining groups you are in and making friends with your friends are subtle ways for her to keep track of your activities. It could also be as obvious and scary as driving by your house at night. New technology makes it possible for her to check up on you multiple times per day on social networking sites. You may want to change your old passwords, too -- your ex could be spying on your email or voicemail messages.
Your ex may suddenly fall into a sour mood after observing you talking to the opposite sex. Does he now ask if you are dating every guy you talk to? Are you wondering how he even notices every guy you talk to? He is dreading your next relationship. He might lash out by way of midnight texts or "drunk dials."