What Causes Black Clumpy Period After 1st Ivf Cycle?

my 1st ivf cycle was positive but then the pregnancy failed just days later. I had a light bleed for a few days then a couple wks of black tar like clumps. Last wk ivf cycle 2 failed with neg result this time. However i have same aweful black clumpy period. I was using crinoen but stopped 4days ago when the blood test was neg. Should i be concerned?