I lost my original post.....
I was able to breastfeed my children for extended periods of time without any obvious bad effects, but then I don't believe I've had any major bone loss either. http://www.breastfeeding.com/
This is a place I am long familiar with although I don't know what it's like now. I weaned my last one almost four years ago, so it's been awhile. They did have a good lactation nurse answering questions at one time.
It must have been scary and very upsetting for you trying to do what you thought was best for your baby and to be getting more ill in the process. You did a good thing and even better, you've taken care of yourself so you can be here for your child in the future.
You are a good mom!!!
I hope you had a good appointment. You do have options. You can nurse in the beginning to help establish an immune system in your baby, then go to formula and breastmilk until six months, then switch to formula or... It really depends on the decision you make based on the knowledge from your doctor and what you feel is best.