doesn't cause diarrhoea
.It is most likely due to food poisioning and should be all right in next few days.
For postponing your periods,do the following...
The day your pack of active FEMILON PILLS finish,start another new pack from very next day.With this Thete will not be any pill free days.
Keep taking your new pack till the time you want to avoid periods.
The day you feel that you can have periods,stop taking FEMILON and then you get withdrawl bleeding after few days.