No periods after child birth & not breastfeeding why???

[savingmylife]

Hi

On May 7, 2007 I had a healthy son.  I bleed heavily for about 3 days then it slowed up & stopped within about 2 weeks.  I breast fed for no more than 2-3 weeks & mostly it was expressed milk as my son wouldn't take to the boob so we went to formula after the expressing made my nipples really painful.  

Ever since I've hardly had any periods.  When they do come they are massively irregular.  Note - they have always been somewhat irregular when I haven't been on contraceptives - which I am NOT on now either (like, between every 3 & 1/2 - 6-7 weeks, each lasting abt 5 days).  However, never as irregular as this.  I have not had a normal period since giving birth.  I have had about 2 heavy periods lasting 1-2 days.  Initially there was some spotting for about 5-6 months, like just a tiny bit of blood but only for a day or 2 at the most, but really infrequently, maybe I'd go a week, or 6 weeks.  

It is also important for you to know that during that time I have been addicted to prescription drugs.  Between Jan 2004 (including throughout the entire pregnancy) & Sept 2008 i was taking about 800-1000mg of slow release tramadol.  From Sept 08 - Jan 09 I was taking morphine about 150mg injected a day.  I know opiates can be a cause of irregular periods.  I am now on Suboxone of 14mg per day after I sought help for my drug addiction.

Questions:

1)
Would you think the lack of periods would be due simply to the drug abuse alone?????? If so why were my periods much more regular before child birth even when i was taking the tramadol then??  Did child birth on top of this change things??? It was more than a year after the birth I switched to morphine so I'd have expected things to go back to how there were before under the tramadol before giving birth.

2)
Can I still get pregnant in my situation with no periods & on suboxone?????? Considering I'm not on contraceptives too.  

3)
How can I tell when I'm ovulating & when the window is to get pregnant with no periods, or hugely irregular ones to go by?????  I am NOT wishing to get pregnant as I know pregnancy & Suboxone don't go together.  I just want to know.

4)
Could I be infertile due to the drug use & that's why I'm not getting periods???

Thanks