I don't have an answer for you, (I know, no surprise), but maybe I can offer some info?
I'm bipolar rapid cycling, normal cycles are 4-6 in a week, but sometimes slow down to a more sane once per 7-10 days. I had a problem once where I was cycling more like a butterfly, multiple times in a day, it was really tough on those near me. I was also on a higher dose of Cipralex, a SSRI. My Pdoc figured it was the SSRI causing the problem and he was right. As the dosage was dropped my mood chart stopped looking like a richter scale machine. Maybe one of the meds you're on is playing a part?