I don't think that medication can affect menstruation. Mood can certainly have an influence though. I also suffer from PCOS and am menopausal. I would go for months on end when I wouldn't have a period and then when they came they were horrendous. I had coils and eventually a hysterectomy. I even felt that my mood was influencing my cycle and I could control it. Definitely talk to your GP about it
I'm editing this as I know some mood stabilisers can affect mensturation and fertility.