N.K.
I found this online:
"f you do take pseudoephedrine and notice a drop in milk supply (many moms do not, but research shows that it can decrease milk supply by as much as 24%), simply stop the medication and take measures to increase milk supply - the problem should resolve fairly quickly. "
http://www.kellymom.com/health/meds/cold-remedy.html
I hope things will resolve quickly for you too!