Just wanted to tell of my experience with plugged ducts/mastitis while nursing my son. It was continuous for 9 months - I never stopped getting them. It was extremely painful(every day), and I, too, would pass stringy thick clots at times. Nobody every figured out what the cause was - one of my "theories" was extreme stress. Would this Mom happen to be under alot of stressors? Antibiotics would help briefly(very briefly). I never had any problems when nursing my daughter(who is older). One of the other theories I had, was that maybe I had yeast towards the beginning that entered my breast through a crack, etc and I never was treated for yeast(centrally - only topically). I hope that helps some. Sincerely, Linda Marie Bradley, RN,BSN,IBCLC