well ok. i had weird periods. im on my second period since my baby born via c section. my first was gross long (21 days) heavier than anything. my second which im have finished i think but im still spotting. has been 11 days. i saw dr n gynos had ultrasounds done. dont be worried se ur dr just to put ur mind at ease. i lived at the drs at one point. if its placenta (iv had placenta left behind with my second child) it would be red large clots the size of golf balls and bigger ( mine were the size of madarines) and ultra sound confims any. but yellow spongy stuff wouldnt be placenta.