It is not Advisable, especially if it makes your baby fussy. It took the tummy 9 months to get to that size. So you will need to be patient as well for it to go down. Incorporate more healthy meals in your diet. Moreover, if your tummy wasn't flat pre pregnancy, don't expect so much then. You can also incorporate some exercise into your routine and be patient as well. Their is no fast way to it really.

This might not have anything to do with breastfeeding. It could be due to rash or skin irritation.