sorry to hear you're having a crappy time
it must be doing the rounds because i was behaving like a complete nightmare myself yesterday!!
i know you've said you've recently started on a shake diet - do you think that's part of it? i.e. has it just been since you started on the shakes? maybe it's your body adjusting to the change?
losing weight & making lifestyle changes is an emotional process though - no matter how you're going about it!
i hope you get some time to yourself for exercise - cos that's guaranteed to help your mood