I'm not being rude but I think half of the problem in those photos are your breasts! You don't look too big but you're rather top heavy (you lucky cow lol)
OK I shouldn't laugh, but when it comes to it weight is weight, doesn't change the load the horse is carrying!
Two thoughts though:
I am all over big, and I have to say I was horrified at the first dressage video I saw of me, taped from C, and the trot down centre line towards the camera, well all I could see was breasts
Second thought, I have a riding buddy, same age, height and weight as me, but she carries a lot of weight on her breasts, I think she looks great on her little Morgan, because she is smaller than me in most areas, and when she straps the girls up well, she looks much better than I do...jealous.
OP, better to ask the people who know you and can watch you and your horse in real life how you two are suited, so difficult to tell from still pics, especially the angles you have given us.