Ali- Don't feel like a bad mum, they are bound to get cold/sniffles no matter how much we try to protect them from it. A midwife at the hospital told me that on average a baby will get 10 colds in their first year, not sure if it's a slight extension of the truth, but that's what she told me!! Chin up have you tried the fess to try and thin the mucus might help her breath better!! or even have a shower with her , the steam will help loosen her the muck!!!