What Causes Delay In Periods And Brown Discharge After Having Unsafe Sex?

For the past year I have been experiencing some issues with my menstrual cycle. My most recent cycle was Jan 17th -23rd following after my cycle, I had unprotected sex with my mate and ended up taking a Plan B on Jan 27th, 14 days from date I had another cycle. Since then , I have not had a cycle since the first week in Feb. In March, I passed a brown sticky string and spotted for two days, and this month I have had a really thick discharge assuming it was a yeast infection or Bacterial Vaginosis, but today I experienced a thick pinkish discharge. What could this be? Could I be experiencing a cycle?