I am 29 years having 2 years baby with normal delivery. having endometrial cyst of 3.8 on left ovary. I am having endosis 2 mg medicine content only dienogest from past 2 and half months to cure endometriosis cyst. From past two months my periods were on time and there were no side effects of medicine. I have never missed my periods. But this month first time I have missed my period it has been a week. Today I check pregnancy test but its negative as well. My 3 month course of medication ends on August 17 .My question is my having again pain on same left side. why? I use medicine regularly. Secondly is there any chance of pregnancy ?My period were always regular on time on 20th to 22th of every month but this time missed. please guide.