I never really realized how many cf women even had children until coming to this site. I was told I couldn't have children, then I was told it was possible but would be very, very difficult to have children and then finally, I was told to use birth control until I was ready to start a family because it was just as easy for a cf woman to get pregnant as anyone else. I'm not so sure about it being easy, judging from many of the IVF stories I've read about here, but nevertheless, because I'd always been told it wasn't a great idea (or was impossible), I never planned on having children and I really thought I was fine with that decision.
It wasn't until a couple of years ago that I finally realized what everyone was talking about when they said they had that desire to be pregnant and be a mom - maybe it's hormones or the biological clock or who knows? But now that I actually DO want that for myself, it's too late, I'm too sick - even for adoption. I don't have the energy to care for a child - cf is all-consuming, and I could never half-a$$ the job of being a parent which is what I would have to do if I had a child at this point. I wouldn't be able to devote the energy and time to that child that I believe s/he would need and deserve.
Still, we can rationalize our choices all we want, but just as sitting and crying about it won't change anything and doesn't help, convincing ourselves we've made the right decision not to have children is not all that comforting either; it doesn't erase the fact that we have been robbed of yet another of life's great joys.
So no advice from me, Julie - wish I had some for sure. But you are not alone and sometimes, just knowing that is enough.