I'm sorry you are having these problems but you know what? I agree with the animal shelter. If you are working full time, it's not fair to the puppy or to you for that matter. You would come home so tired and then feel guilty if you don't walk and play with the puppy. Puppies need a lot of attention and guidance, and can be quite destructive if left alone a lot.
I got a puppy when I was working. We tried to keep it in the kitchen while we were at work but it broke loose and literally destroyed out furniture...chewing holes in the sofa and chair and also chewed a hole in the carpeting! When it was six months old we had to get rid of it. She went to a home that had three pre-school children and that puppy never chewed a single thing! All she needed was some loving attention during the day. My heart was broken, my wallet was empty, but I learned a great lesson.
If you want a pet, you might consider a kitten. Most apartments allow cats, too, and many are absolutely adorable and quite loving. I have a dog and two cats and all are a joy to me. BUT I am retired and can spend the time with them.
I do hope you start to feel better soon. Hopefully the doctor will have great suggestions for you.
Sherrine