#1 He Talks About Her Non-Stop
If he talks about her a lot in conversation and her name continuously comes up, along with things they did or shared together is probably still hung up on her.
#2 Compared You With Ex
One of the main reasons a man might compare his new girlfriend with his ex-girlfriend is because he’s not over her. Whether it be about the way you look, the way you act, or the things you say, he directly connects your actions with hers.
If his ex is being compared to you, he’s not over her.
#3 Checks Up On His Ex On Social Media
He’s always up to date on what she’s been doing. He likes her pictures on Instagram and Facebook. Her profile always comes up if you see his search history.
#4 He Texts Constantly
He always checks his phone. Whenever he talks to her he acts strangely. He refuses to share what's in them which may leave you wondering if something's up.
If he refuses to detach himself from her because they're "just friends," then it may be time for you to wake up to the fact that a man who is really over a past relationship would respect you by not "casually" talking to his ex.
#5 He Can't See Her With Someone Else
Maybe his ex has recently started dating someone new and he has been in the most horrible mood since then. She's moved on—you know because you checked her Facebook status and she's in a relationship with someone new. He's checked too, and he doesn't like it. He is without a doubt jealous, and jealousy is the number one sign of having feelings. If he keeps bringing it up, ask him why it bothers him so much.