Are Pieces Of Tissues With Heavy Bleeding During Periods A Cause For Concern?

I did not have a period for 7 weeks. I did not take a pregnancy test. I started bleeding heavily, and noticed two pieces of tissue that were not blood clots. They were about the size of quarters, and pinkish/whitish in color. Almost egg white consistency. I am also having severe back pain and cramps, along with a migraine. What could the clots be, and should I be worried?