My periods are due on the 1st of dec. I'm going on a trip with my husband from 31st to 2nd. So I'm planning to take Primolut N to postpone my periods. That is I'll be taking it from 26th to 1st every night. If I'm planning to have sex on the 31st and 1st, when should I take the I pill? Should I take on 1st and 2nd morning? Or 2nd morning is sufficient? Also, will primolut N react with I pill and cause any problems??

The I pill is not for regular use and other forms of birth control should be used for regular planned sex. It also should not be taken two days in a row.
It will not be as effective for the 31st or 1st, if taken after sex is finished on the 2nd.