Once feeling better and all healed find out if there is an encore program or something near you. You could get a gp management plan done and have a referral to an exercise physiologist once you feel ready. Failing that just start with 10 mins walking...and build up. You could do this morning and afternoon when feel ready then start increasing time. I also used to go to a warm pool and just do some walking or very light swimming. Little steps. I also found frequent rests when out...find a seat etc helps you to keep going. You'll get there.
My upper back also ached a lot but has settled now. I wondered if it was all the resting ....standing to cook was agony. But it has gone now. Our muscles have been weakened by the surgery...gentle breast stroke has really helped mine.