Many women who use opiates stop having periods but there is no evidence to show that this is a direct cause of having opiates in their system. Methadone does not affect  the levels of the hormones that control menstruation. It is much more likely that the periods
have stopped because of stress, poor diet or weight loss
It is important to remember that even if you are not having periods you can still get pregnant.

At any time during your script but especially at the start or during detox when desire to have sex may increase you may get pregnant

Apart from protecting you from HIV hepatitis and other sexually transmitted diseases condoms could still stop you getting pregnant even when you aren't having periods. They should he available free from your local drug service. Advice on condoms and other forms of contraception should be available locally from drug agencies, family planning clinics and GPs.