Weight Gain, Had Taken Primolut- Nor, Negative Pregnancy Test. Cause Of Increase In Weight?

My last period was 17/7/2012 and before 27/6 and 27/5 respectively. My doctor recommend me -without any gyn exams-primolut nor and after this treatment we re going to take the proper exams. Plus, on July, whereas I had my last period, I took exams to get a job and all the proccess made me very anxious. Afterwards, I ve tried to lose all the weight that I ve taken during my exams (4 months) and since august I m exercising (swim, walking, etc.) every day. I m bit worried about the primolut nor as I had never use them before. Please, bear in mind that I had done a pregnancy test from the pharmacy and I saw the negative line. I m looking forward to hearing from you..thank you indeed.