If I were you I would get myself into PT if you are not already. They can help you with osteoporosis and give you the most specific, beneficial exercises for your condition.
I know "chair" yoga is good for me. It might sound like a piece of cake but does the job for folks like us.
And I would get medical clearances from your physician for using light hand weights...like 3 to 4 pounds. And, of course, a walking program. Even 20 minutes several times a week is good...don't worry about your speed if using a treadmill. Weight bearing exercises are all good for osteoporosis. I know definitely for prevention but since you have been already diagnosed you need to talk over an exercise program with your medical care providers. You don't want to do more harm than good! I have never heard of Classical Stretch so I can not comment on it.
Don't despair - you will get yourself back on track!