No periods since a month. Questions.

Hi, i had safe sex with my partner on 9th of march and taken ipill for safe side on 10th within 14 hours. I had bleeding but not a regular periods flow after 9 days from it which was on 19th march continuously for 4 days. When i consulted doctor, she said it's periods. The next month due date was 20th april. I didn't get my periods. I also took teice urinal pregnancy test, but negative. I consulted doctor on 26th of march. She asked to go for abdomen and pelvis scan. I did and the reports were normal again. She asked to wait for periods and again take a urinal test after 10 days. I took one on 8th of may, and again negative. I'm having cramps just like periods but i still didn't get my periods. It's been more than 30 days. I'm not using any medications. I don't have any previous health issues. Please help me with an answer for all these questions.