I'm doing a dairy-free month as an experiment. About a week in and I'm fine, no cravings. Why don't you try following your doctor's advice, and if you don't feel any better and/or you're craving butter, introduce it back into your diet?
Also, forget margarine. Coconut oil is what you need. It works for me in all the instances I would've once used butter, but it does have that coconut flavor to it. Personally, I like the flavor, but I could see how some might be put off by it.