Delayed menses regularly. Guide us.

My fiancee is experiencing delayed menses for a few months now. This time it is over 15 days due. We thought it to be because of the stress and drastic change in routine. She had to face the demise of a very dear family member. Also, she is studying for CA Exams. So she has been studying all nights long and sleeping during daytime. The diet wasn't proper as well. So we tried and changed all this. But when it didn't help much, we consulted a doctor and took medication as prescribed. Tonight the course for 3 days is also complete. But still no menses. She is experiencing body pains. After the medicine the pains have increased a lot, especially in legs. But no menses. We also had unprotected sex a couple of times. So we were worried if that was the case. But she took the pregnancy test thrice. Negative each time. Also, the medicine prescribed was norethisterone. I checked that it is also a birth control pill. So I don't think that should be the case. But still no menses. please guide us.