Hello, I pill can cause heavy bleeding,, bleeding for longer days than usual periods. Sometimes it may not cause bleeding, or you may see just spotting. Nothing to worry this itself will stop (if I pill had taken with in 72hours of unprotected intercourse). And your periods will be irregular for one or two months and regular period date may change. One the other hand if bleeding is too much (changing more than 3pads a day), if you feel pain,, if you get giddiness please consult gynecologist.