Try Yoga..especially the breathing techniques.
But I found out myself personally, I have a 3 month cycle.
What I mean is about once every 3 months I'll get a very low mood, like what you are referrring to. I used to panic about it, until my boyfriend at the time told me "you are like this about every 3 months or so". Now I panic less, and ride it out.
I remember reading about Liane Holliday-Wiley has to take time out from the world, to the point of shutting herself away.
It's a combination of Asperger's and PMS symptoms, in that AS brings out any mood difficulties more.
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Dory: "Just keep swimming. Just keep swimming. Just keep swimming, swimming swimming. What do we do? We swim, swim, swim."