Are you performing your Core work correctly? Do you know what the first step is when performing core work - hint it's not hundreds of Ab Crunches!
It's activating a particular muscle called the Transverse Abdominis. This is your first goal as this muscle is crucial to your entire core working correctly.
So, start with this video. Stefanie explains it perfectly. Practice activating your TA and then you can start adding the activation into your regular exercises i.e when squatting. Eventually, your core muscles will start working automatically and your core will be supporting your entire body the way it was designed too:-)