My baby doesn't often take a pacifier, but occasionally he will. I've noticed lately that once in a while, putting in the pacifier will trigger his gag reflex and will sometimes even cause him to spit up. I've tried using the "mam" pacifier that we received in the hospital, as well as some Avent ones... he's been using all of these happily until now, although not often. The gagging is a new thing and only occurs sometimes... What could be causing it? Is there anything to do about it?