I skipped everyones responses (forgive me if I contradict or repeat).
From the angle of your photo I would say the saddle is definitely part of your problem because it appears to be too small for you. Are you using the western pad because it's all your have or to try to make the saddle fit better? (I'm curious). I think an english pad would work better with that saddle.
What is your plan for riding? English or western or you really don't care?
From what I can see in your picture you need to shift your lower leg back a bit and it looks like you are sitting completely on your pockets so you need to open your pelvis and sit a little less on your bottom. Your body position along with the poor fitting saddle is most likely your issue with the movement. Is there anyway you can post a video?
PS - I hate bareback pads (never could get used to them).
You didn't contradict anyone, but offered similar advice :)
I was using a western pad to see if it'd help. I've used an English for the most part in the past so I figured I might as well try a western one and see how that would work.
My plan for riding is that I'd love to go into English riding, but at this point, I also just want to ride in a saddle that fits since that's the biggest issue. And there are things I want to do in western as well. So I'm pretty happy to simply be able to ride, but at some point in the future, I want to do some more english, especially jumping or XC. But again, I do want to dip my toes into everything.
I have been considering video some moments when I'm riding to get more tips and advice, but I haven't been able to do it just yet. I'm also going to have a riding lesson tomorrow with someone knew who is apparently blunt and honest and that's what I need so I'm hoping I'll get questions answered by a trainer who'll see me ride in person as well.
And thanks for the tips about how I was sitting, I'll definitely work on being more aware of my posture and such as well!