Husband showing interest in his ex

So we’ve been married 6 years. My husbands ex girlfriend just got married. He’s not friends with her on any social media. The breakup was bad and was all because she faked a pregnancy. Well he has some mutual friends with her on Facebook and he claims he just saw a post from one of her friends the other day that she got married. Since then he said he wants to add her on Facebook so she can see how well he’s doing, and he made a comment saying I hope she’s posts when she finds out she’s pregnant so I can comment on it and say “are you sure.” He’s sounding really immature and jealous right now. His thoughts are pushing me away as a wife, making me feel like he’s still got feelings.