Please help! Advice! Suggestions! Experiences of heavier bleeding with tons of clots!

Crystal • Happily married since 3/28/14, ttc #1! It`s time to start growing our family!
So my hubby and I have been TTC for 8 months now. This month, I seriously thought I was pregnant until AF showed up right on time as always. This time, I am bleeding much heavier than usual and noticed tons of dark clots. I also had a little bit of cramping which I usually never do. Does anybody know what this means? Thanks in advance!