Boy do I ever suffer from PMDD (for years). I have the horriable mood swings every month 2 weeks before my period. Some months worse that others, but I haven't skipped any months.
One thing that has helped SO MUCH is that I take Sarafem just 2 weeks before my period, and nothing once my period starts. It had keep me sane all year! But the chocolate bar sounds like it could help too, it certainly can't hurt (except my waistline) LOL