Took I-pill Twice After 2 Unprotected Intercourse, No Periods For 4 Months Now Only Blood Stains, Then Heavy Bleeding. Why ?

I took I- pill and had periods if few days.....after 15 days I again took I-pill after an unprotected intercourse and again got periods in few days....both time periods were normal....after that I didn t get periods for 4 months but in between few times had some blood-stain....then for about 10 days few drop bleeding continued and afterwards I got proper periods....initial 2-3 days were normal....but now its sixth day with heavy bleeding...please help me!! P.S. - usually my periods last for 3 days....I had irregular periods thus had Yaz for 9 months as prescribed by doctor