Plan B and Never Ending Period

Hello ladies,

We had a slip up a few weeks ago and I took a plan B to be safe. I attached a screenshot of my month. I had just finished my period when I took it and several days later started a light and very dark, almost black, bleeding. That turned into a regular period. The flow became very light and dark again after about a week. But, yesterday (I'm supposed to be ovulating) I was having cramps and other PMS signs and my period started up again extremely heavy.

I'm wondering if any one else has experienced this and when you think I should start worrying and head to the Gyno.

Thanks in advance :)