Thanks for the query.
Emergency pill can cause menstrual irregularities as side effects.
So the heavy flow and inter-menstrual bleeding
you are expecting could be because of these.
For more details:http://srsree.blogspot.in/2012/08/emergency-contraceptive-pill-short-term.html
These side effects will subside soon with out the need of medication.
But if the symptoms are persisting and bleeding becomes heavy better to consult gynecologist once.