First let me clear up something for you. You have gone through menopause. You are postmenopausal. If you've gone one year without a period, you are postmenopausal. That means that your ovaries are not producing estrogen. That combined with your eating disorder depletes calcium from the bones.
You should be looking at T-scores instead of Z-scores. You definitely need the calcium and Vitamin D. You also need an osteo med. You are waaaaay too young to have to deal with fractures. Because you've had one fracture that alone puts you at double the risk for another. Fractures impact quality of life. With osteoporosis, they heal very slowly and often irregularly.
Birth control pills will help, but you need more. You can do that and something else. I doubt that your bone density will ever be in the normal range, but you can hold off fracturing.
I would suggest a couple of things. First I'd go online to the National Osteoporosis Foundation website (
www.nof.org ) and order their booklet "Boning Up on Osteoporosos." It's $6.50 and gives you all kinds of reliable information. We use it in teaching our osteo rehab classes. There's also other info available for patients on the site. Play around with it and get informed - especially their official statements about use of the osteo meds.
Next, I'd research the meds and with your doctor, choose one. You can't escape it and expect to lead a fracture free life. Diet and exercise help, but with scores that low and one fracture under your belt, only meds will do what you want to happen. My personal suggestion for you, with your absorption complications and hesitancies, would be Reclast. That's the annual IV med. It gets very good results in patients. You could do this and birth control pills.
I'd also get some instruction on proper body mechanics. The booklet gives you some info, but a physical therapist can assess you individually and really help. There are some definite "no, no's" you should be aware of.
It's good that you're this young and taking charge. You've a lot of years ahead and you want to be independenet and active.