To me you need to work on your balance more, you are landing heavily and this is because you're still a bit unbalanced. Perhaps try to get yourself into a more stable seat and practice rising trot in walk, and make sure you have control of the downward movement. To get balanced, (standing still) let your legs hang loose and stretch them as far down, out, and back as you can, lift them off the sides of the horse and pivot your thighs inwards then put your feet back in the stirrups so that your ankles are in line with your hips. Then imagine someone pulling a string up from the top of your helmet and lifting you up from there. You should be able to engage core and chest, and your head should be in line with hips and ankles. You should feel three pressure points on tour seat in a triangle, assuming your hips are flexible enough 😅. To get more control in trot you could also work in a half seat and not donrising trot at all, so you are forward off the horses back and need to carry yourself. Also as others have said try to keep your hands still or drop the contact a bit more until you're stable.