Nursing screwed my posture!

Ive been a new grad for about 4 months now, and I feel like my legs arent connected to my waist which isnt connected to my upper body which DEFINITELY isnt connected to my arms. My posture sucks. I have always walked well, i workED out everyday, great physic and blah blah blah, but now when I even go to the gym, I leave there with aches and pains, i dont workout with my core cos my legs are doing their own thing, and my arms are in its own world. This is serious. I can;t comprehend. when I sit, I SLUMP so badly, i have to remind myself, sit up. it's pathetic. never been like that. I became curious and studied some of the nurses and how they walk and and a majority of them have some limp or tackiness about their walking. ugh. why?