I can't tell for sure, but the saddle doesn't look like a great fit, and it's super far forward in my opinion.

You look so stiff that the horse is bracing uncomfortably against the reins. Relax! I did the same thing for years, lots of seat lessons helped!

You also look like you're stiff in your hip, maybe from thinking "heels down"? Try "toes up," it helped me!