My upper back is looking like it has a curve in it almost like kyphosis, when i try touch toes my upper back curves, I am aware of this and try keep a straight back now, when I sit at 90° angle my lower back gets rounded out and back, but to me it feels like it’s straight, my yoga teacher said its probably from tight ham-strings can anyone else confirm , will post photos in comment section
Hi @Sammyray and welcome to YogaForums 
I cant shed any light on your situation but hopefully soon one of our more experienced members will comment.
Good luck with your practice 