Help fer building upper body weight

Suffer4beauty

Quick backstory: I was always in AMAZING shape until the pregnancy of my 3rd child. Many problems meant doctor told me to eat EVERY time I was hungry to help baby grow, and ceased my exercising. Went into labor, baby died during labor and my torso was pretty banged up during the delivery due to the interventions they were trying to do... (she's in heaven, I will meet her one day. I'm just writing the story because I am embarrassed about where I have come to and I am "justifying" the reasons that led to it).
Due to eating tons of calories with bed rest, and not knowing what was pregnancy weight gain (fluids/baby) and calories - well, it was a lot of calories - I gained tons. Sadenss and physical recovery meant I didn't pick up routines again until 6 months later. But 3 months after that, I was pregnant again - eat/no exercise. Baby born healthy.
But now he is over a year. I was only 140 pounds when I first got pregant with the "real" number 3, but now I am 200 pounds. I've also had several injuries - including a starined chest muscle.
So it all comes down to this: I've never had to gain muscle/loose weight from a point of being so not fit. Push ups are impossible (sadness). Even modified push -ups, my back still struggles not bowing. So I think I need to start a different way with starting to build all those muscles more individually. What individual exercises may help me build some base strength? I know a few things, like maybe lifting dumb bells in different directions and up over my head for triceps... but what else?