I started with flat nipples (one slightly inverted) and am currently breastfeeding my 11 week old son who comes complete with Down syndrome (tiny palate and broad tongue) and a nasal cannula from his home oxygen. He has laryngomalacia (floppy airways) so we stop for breaks when he gets gaspy, which only happens during the day when he's thinking too hard about it instead of going with the flow.

It's not always hard.. My daughter I found it difficult, but I was younger, had personal space and aversion issues, and only lasted 4 months. This time around is so much easier. I still can't pump as it hurts too much, but because of that I have a tin of formula in the cupboard in case of an emergency and I can't breastfeed. (Emergency babysitter, etc). I haven't had to use it yet but it's a reassuring backup when you don't have a freezerful of EBM.