Do you think this could about more than the occasional pot use? You said you lost your job recently, is she venting her frustration about being pregnant and you not having a job, but blaming it on the pot? I think talking this out is the only resolution. Some states have medical marijuana, if you had a prescription would that change her perception? Do you think it might be the hospitalization that is the cause of this? Maybe you didn't change after you got out, but her perception of you did. Some times we see what we want in people, and when that breaks down we think the person has changed. Example when you have a friend and then they betray your trust, you don't think they are the same. You think the person is trustworthy until they betray you, and then you think they are a liar, thief whatever. The person was always the same, but your perception changed. Could something like that be happening between you and your wife? How does she feel about your illness? Does she accept it and support you or has she became more distant after you got back? My only suggestion is to have a calm honest talk and tell each other what is bothering each of you. Marriage counseling can be another solution. A mediator, and someone who can explain bipolar may help her see your struggle. I hope you find a way to work thing out.