Ouch on your hip!
I've got two areas of 'severe stenosis' myself - my doctor told me that I have an 'eighty-year old' back to go with my 'eighty-year old' knees.
I just finished a series of three epidural injections about two weeks ago and go back to the doctor today. Luckily my pain is about 90% better. I'm so sorry your relief didn't last! I don't know what my next step is if mine wears off too soon?
Even though it hurt like the dickens, I exercised every day throughout the months leading up to the diagnosis and throughout the injections. It was very hard at times and I had to adapt what I doing, but I was afraid if I stopped, I'd never start again.
The only piece of cardio equipment I could use was the elliptical. Even the bike was too painful, so I stuck with the elliptical. But sometimes I had to drop the resistance when things were especially painful.
I added a ton of ab and lower back exercises to my routine and really think that's helped by strenthening my core muscles.
Has your doctor suggested physical therapy? Have you tried cardio other than walking? Do all exercises hurt?
I'm so sorry you're going through this - I really feel your pain!!