Severe pain in lower part. Bleeding?

My G.f has taken 3 i-pill in a month. Me and my g.f had unprotected sex on middle of the April but i didn't cum inside her and then within next day of sex she took i-pill for safety reason. After that she again took I-pill on 1st week of May because of the leakage condom. After that miss-periods had started. Then we again had done on 20th May in withdrawal methods and she again took i-pill within 2 days of sex. But the last week of May was hilarious time of her. She suffered so much pain. Then on 2nd June she had her normal periods. After that we had sex so many times in this June and that was protected. As naturally on 3rd July the period has started again but the bleeding is heavy compare to her normal cycle and she  having severe pain in thighs,lower back and lower abdomen. What could be the reason of this severe pain and heavy bleeding?