What Causes Short Periods And Stomach Pain After Taking Otovlan?

i took otovlan tabletys at the end of aug, after taking them i came on my period for 3 days only, which is unusaul as i am normal very heavy and my period normally lasts for a week... since then i have not had a period and was due on monday, i have hoorrendous pain in my stomach and have had for 2 days now? what could this be?