Need to delay periods. Will be it safe?

Hello, I'll let you know my problem in details. On 29th April i took one i-pill due to having unprotected sex. After that i got my periods on 9th may which was like two days delays from last period which i got on 7th April. Now again it's like i want my period to be after 7th June as am going on my office work out of town from 2nd June to 7th June. And it is really important time for me to concentrate as it is about my future. So is it possible to take any tablets which can be helpful to delay periods. From when I should start it. From last 4 months am getting almost regular periods, like 1-2 days up down with heavy bleeding for 3 days, having cycle of 28 days. These time am worried as last month i had Ipill. One of my friend who is pursuing study in medical field only suggested to take tablet named as a 'primolut n'. So am planning to take it on 3rd, 4th, and 5th June. Will be it safe? Or any other tablet you can suggest me. Any responses would he really greatful.