Getting my swim strength after back injury

Not 100% sure this is the best place for advice. However, I’ve yet to find another forum. I am 45/F, used to swim competitively from Jr High - early college. The work and life got in the way. Five years ago I injured my back and now have disc degeneration in my lower back. Two years ago I got back in the pool and eventually went from 2 laps to 50 (25 yard pool). Then really got to feeling better about my swim and back after a year of sticking to it. Then work got in the way again and I didn’t put in the time like I did for a year and had another disc blow out. So on 11/20/18 I had a back surgery and 12/19 made it back in the pool. I’ve been swimming every day since aside from one day off each week. I am starting over again, can only get to about 850 yards and (3) sets of 15 ladder pools before I run Out of gas. Today, after my swim, my whole body is aching. I swim at my gym pool, which is indoors and at about 77*. This brings me to these boards looking for advice. Am I doing too much at once? And any other suggestions you have are appreciated!