I just wanted to say I'm sorry for the terrible time you are having. What should be the most exciting time of your life probably just became the most scary. Having been there, I can somewhat understand what you are feeling (though I realize every situation is different).
My thoughts on amnio... I know many people feel that the only reason for an amnio is if you plan to abort the baby. I very strongly disagree with that. I didn't know my first daughter had CF until she was 2 1/2 (no family history...I didn't even know what CF was until I started reading medical books trying to figure out what was wrong with her). Then shortly after her diagnosis, I found out I was pregnant again. I decided right away that I would have an amnio. The thought of aborting never so much as entered my mind. For me it was to be emotionally and physically prepared for what was coming. I knew already that having a baby was a very emotional experience. The hormone levels going up and down and the stress on your body and mind can be overwhelming. I didn't want to double that by having a new baby and a new CF diagnosis at the same time. If the diagnosis was going to happen, I wanted it ahead of time so I could have a few months to accept it and make peace with myself. That way I could focus on enjoying the new baby when she arrived rather than focusing on the CF. For me it was well worth it. I found out at 17 weeks that she did in fact have CF. It was hard...no doubt about it. Even harder than the first diagnosis in some ways. However, I had 5 months left to deal with it and by the time she was born, I was prepared. I didn't focus on the CF, only on her.
There are other benefits to knowing ahead of time, such as being aware to look for bowel problems via ultrasound, being prepared to deliver at a hospital which can care for the baby should the need arise, etc. I'm not saying everyone should have an amnio...it is very unpleasant and for me was quite painful, but I would certainly do it again. I just wanted to say there are some benefits of an amnio other than the option to abort. It is most definately a personal decision and I wish you the very best whatever you decide.