I use Flixonase too. Whilst breastfeeding I was told not to use it. I was really suffering so I did a bit of research and found out that the reason they tell you not to use it is because there has been no research into the effect of use on pg/breastfeeding women. This doesn't mean that it will harm your baby, just that no-one knows so it's better not to try.
Just for the record, I was suffering so bad I did use it now and then, - sorry if that makes me a bad mum in anyone's eyes but unless you've suffered from bad hayfever you don't know what it's like! Anyway, nothing bad happened! I felt better, and I was a better mummy because I was a functioning mummy. If you can keep it to an absolute minimum I don't think there's a problem xxx