Hi there, has your regular cervical mucous changed at all? My first thought would be BV or thrush as well. So if you're completely sure that your discharge is normal the rest of the month, then we can rule that out.
I'm not sure what it could be then... I had the IUD and too had increased flow (which never normalized for me, btw, in the end forcing me to have the IUD removed). I also developed constant thrush, but the actual menstrual blood's odor didn't change.
I'd wait and see until your next period. It might be the copper is reacting oddly with your fluids, don't know.