Hi, Thanks for posting in HCM. Noriday contains norethisterone. It is progestogen-only oral contraceptive. Side effects which could occur include some cycle irregularity during the first few months of therapy like spotting or breakthrough bleeding and amenorrhoea. Other side effects noticed include: breast discomfort, GI symptoms, rash, migraine, depression, fatigue, nervousness, disturbance of appetite and changes in weight and libido. If you misses two consecutive periods, pregnancy should be ruled out before continuing the contraceptive regimen. Since your pregnancy tests are negative, you can continue the medication. However, if you want to discontinue or change the medication, kindly do that under medical supervision by consulting the doctor. Hope the information provided would be useful.