Metalic smelling breath

Help - I'm 31 weeks along and for the last week or so my husband keeps telling me that my breath has a metalic smell to it. I started taking iron pills about 3 weeks ago - could this be it or could it be something else? I don't have a metalic taste in my moth but I do feel my mouth is very dry and no matter how much I drink, I can't quench my thirst. Any thoughts?   Thank you!