waist trainer perm damaged stomach

[cm]

I believe your lower abdomen got a little weaker due to the squeem doing the stabilizing. maybe had some nerve innervation problems as well ( blood constriction) i imagine if you continue to train the muscle, it will return.

the fact you say you can squeeze hard and control it, is huge. you can make it stronger and possibly re train it to what it was before.
another thought is if you can pose it hard and control it, dont worry about, but i know that is easier said then done