What Causes No Periods Despite Taking Sysron?

hi, i am 35 years old. i have 2 daughters both siceriane. last 2 months i don't have a periods. but this is the first time it happens like this. i consulted the doctor they adviced me to took sysron for 3 days 3 tablets daily. last 3 days i took the tablet. between that i took the pregnancy test that is also negative. but still i don't have a period. what should i do? how long i wait thanks and regards