Choppy trot

My pony has the choppiest trot, but in the two years I've known her, it has always been bouncy. Any exercise/groundwork recommendations to help? I haven't ridden her in a little over a week, and today her trot was extra bad. No matter what I tried, I felt like I was slamming down on her back (sitting and posting). Her fist few steps of trot were fine, then she gets bracey and kinda hollow. She also has a habit of trotting as fast as she possibly can (she used to be a cow pony, so i don't think they cared how she moved), especially when turning, so tips on that would be helpful too. She has a decent walk and a surprisingly smooth canter, it's just the trot that gives me a run for my money 😑😑😑 Also any tips for teaching her how to properly carry herself while trotting would help :)

https://preview.redd.it/dudojpyjhnfe1.jpg?width=4032&format=pjpg&auto=webp&s=a9c3d0ad86a320954834387e52ec32dcace17ef3

https://preview.redd.it/eyqubjewhnfe1.jpg?width=4032&format=pjpg&auto=webp&s=17de4b5a675e68e0fd8729fc63b61ee356d021fd

https://preview.redd.it/v14y7yw3infe1.jpg?width=4032&format=pjpg&auto=webp&s=0f7754b6b73a100cf9f65ed6e5203238fa9c3c3c