Flatlands terrify me?

I want to travel more but have recently discovered I get dizzy and panicked when I travel to flatlands. Not just in the car, but like while my feet are on the ground and it’s flat I have so much anxiety and fear gravity will stop working. I’m in my 30’s and know that’s not going to happen but my body can’t help but feel that way. I have a few diagnosis but NONE of them explain this weird new problem with flatlands. Any tips on how to help this? And why in the heck this has started in the first place?