Check yourself for diastisis recti (separation of the transverse abdominal muscles). Its supper common after pregnancy and crunches and planks can actually make your tummy bigger if you have it.
https://www.youtube.com/watch?v=uzIrt82maws
If you have diastisis recti, check out the MuTu program below. Without weight loss, I lost 2 inches in my waist line in two weeks even just with the super easy restorative exercises. I loved the more intense workouts too, but all my progress happened with restorative exercises alone.
http://mutusystem.com
Also, besides the 5 mo prego looking tummy, diastisis is often accompanied by pelvic floor disorder and if you don't strengthen your pelvic floor muscles, there are all kinds of problems that can happen later, like organ prolapse and umbilical hernia. To be honest, discovering I had diastasis recti ended up sending me down a rabbit hole of realizing other problems in my body all boiled down to poor alignment. Now I am working on many issues, but at least I know why I have had so many problems (knee pain, hip pain, tampons falling out).
I'm so glad I have the opportunity to restore the problem before Hernia or prolapse occurred.