Can Mild Breast Pain After Taking Primolut-N Indicate That My Period Is Coming?

Good morning, I was delayed for 9 days since my last cycle. My cycle every month vary but this is the first month I got delayed for more than 5 days. I took pregnancy test but its negative and I went to an obygyne and she prescribed me a primolut n for 4 days. Now i experienced mild breast pain which I start to feel this only when I start taking the primolut. Is this a sign that I will get my period? Today is the last day that I should take the primolut n. Is this pill effective?