hi there, the size of the fibroids mentioned are not very big per se but as you are post partum and your uterus
may not have involuted completely the fibroids are hampering in the normal contraction and clotting of the blood in the blood vessels due to which you are having this heavy bleeding along with clots. As the uterus involutes the fibroid size may decrease leading to less symptoms, so follow the medication and advise given by your obstetrician and hopefully you will be fine in a month or so. Take some iron suppliments to recover the iron lost during mensturation and to avoid anemia
. Take care.