Can methadone make you miss your period?

I started taking methadone on August 9, and I missed my period in August & September so far, do you think it's because of the methadone? Or is it possible that I am pregnant, even when back in August, I took a pregnancy test and it read negative? I've been on a lot of different pain medications and I've always had a regular period no matter what.

: http://alcoholdrugstreatment.info/can-methadone-make-you-miss-your-period