When Will Periods Begin The Month After Taking Pills To Postpone It?

I was given Norethisterone to try to outwit my periods for my hols in April. I normally have periods every 26 days and get terrible black moods which is main reason for delaying it. If I knock this next period back two weeks, will that mean the following one will be 26 days from the bleed or from when period SHOULD have started? IE will it knock my cyle back two weeks? Im worried I will feel even blacker and more bloated if I wait until holiday to delay it?