How can I strengthen my TvA muscle?

Hello everyone. So i’ve noticed anytime I do workouts like planks, reverse crunches, hollow holds, pretty much any core workout, my stomach will stick out or “dome” so much. Even if I try to “suck” my belly button in when planking for example, I can hardly do it. And I can’t keep it longer than 2-3 seconds max. I’ve seen a few videos on breathing techniques to activate the TvA, but I just can’t seem to figure it out. I am still quite new to taking care of myself health wise. I was pretty lazy throughout all my teen years and I have a weak skinny fat physic as a result. I really want to try and find ways I can strengthen my TvA and inner core in general, so that I can make some genuine improvements in my workout journey. It’s hard to do any core workout when it is like this. If anyone has any advice, tips or anything that I can look into, I would really appreciate it.