How Can Amenorrhea Be Treated?

hai i m a medical student from past 2 months i hav not got my monthly periods n 2 weeks back i consulted a gync she prescribed me deviry 10mg for 5 days .but still did not get my periods. abt one year back i received chemotherapy for PNET tumour . after the treatment was over i got regular periods . now i dont know wht could be the cause. please help me.