Weak core

So I’m pretty worried. My son is about to be 2 years old here in a few months. He keeps sitting in the “w” position, he lays on the floor when playing with trucks and toys sometimes not all the time he does this. Idk what’s going on. I read online he could have a weak core because he does have a belly sticking out. I did all the tummy time with him I’m not sure what to do next. Does anyone have any advice? I might check google but like I’m hoping it straightens out in the long run.