Welcome perniciousfirefly! Have you've been diagnosed with bipolar? I would guess yes by the lithium prescription. Are you being treated for post partum depression at all? I would suggest starting to track your mood to see if there is a pattern I have found a great one online at http://www.medhelp.org/land/mood-tracker It has a journal application on it, so you can note if there were any outside triggers i.e. stress, what you ate/drank. Many mental illnesses share symptoms, but there can be a link between drug/alcohol abuse and trying to suppress those symptoms.