Exercise is a good thing - but we have to go at it gently, and build up gradually. Something like a high impact aerobics class is out of the question.
Pilates is a wonderful exercise, and 10 minutes of it is a fabulous start! If you can do 10 minutes three days this week, add in a day next week so you're up to 4 days, and then start increasing minutes. Maybe work towards 12 minutes for a couple weeks. Then 15. Eventually you'll be at 30 minutes, but take your time to get there.
Yoga is similar to pilates, it could be a good choice as well. Find something that you like doing, and it will work for you.
As far as diet, yes, listen to your doctor. One thing I've learned is that I feel best on a lower fat diet. I've cut out meat entirely, though I do occassionally eat salmon, tuna, and (when I'm feeling decadent) shrimp or scallops. Food high in omega 3's help reduce inflamation - which means they can help a bit with reducing pain. Choose whole grains, "REAL" foods (stay away from diet pop, anythign with a list of ingredients you can't read) and monitor portion size.
That portion size thing is the killer. Sites like WebMD and probably Weight Watchers can give you portion sizes. I've found that if I'm getting lazy, I have to go back to measuring things like cereal, pasta, etc for a couple weeks.
Another diet tip? Write down EVERYTHING you eat and drink each day, and the quantities. Keeping a food journal automatically makes you pay more attention to what you're eating. Studies have found that people start making better choices when they write it down, even if they're the only ones who look at it!
~"I find hope in the darkest of days, and focus in the brightest. I do not judge the universe." (Dalai Lama)