PCOS and metformin treatment

I have had PCOS since I started my menses at twelve years old. I started Metformin treatment (500mg twice daily) six months ago. Two months ago I spotted lightly for two days and I am unsure if this qualifies as a cycle. I have been charting my basal temps and could not spot an elevation before the spotting/cycle occurred. Eleven days after the spotting/cycle there was an elevation in my basal temps and seventeen days after the temp shift I had a one week regular cycle. It has been forty-two days since my last cycle and my temp (which does not fluctuate more than .3 degrees during ovulation) has stayed on the higher end of my normal range.
Also. I have had two Vicodin in the past week as well as two alcoholic drinks. The Vicodin is for chronic back pain and is prescribed.When I realized I might be pregnant I stopped drinking alcohol. I do not take any over the counter drugs, herbal supplements, recreational drugs, etc.
Is it possible to be pregnant so soon after starting treatment? Was the first spotting a cycle? Should I be worried about any fetal defects from the Vicodin, alcohol, or Metformin? Is there a safe alternative for pain management if I am or become pregnant?
Thank you all for any advice or answers you can provide.