Either I have PMS, or my empathic shields are being crossed.
The former isn't quite so ludicrous as it seems; men have hormonal cycles as well, and I'm about due a bout of grouchiness. The melancholy and anxiety, though, are way out of normal on that, and it's usually constant and background.
So it looks much more likely that the shields are being crossed. I've been aware in recent months that my inherent abilities are cooling down from the red hot control-the-weather-in-America state of my early twenties, and becoming a more subtle, skilled usage. That's fine by me, because I spent more time doing the magical equivalent of sitting on my hands than actually doing anything.
My first thought when I'm picking up emotions like this is that someone else is broadcasting strongly, due to stress, growing empathy, or whatever. But nobody around seems to match the profile, and while I give some credence to the notion that empathic connections can creep up on you (as in, my middle brother's girlfriend, for instance, who I've never met), these have no feel of unfamiliarity.
So the conclusion is that my shields are weakening, or dropping. I don't want to slam them back up, either, because there are empathic connections I want to leave in place. And since that raw strength is ebbing, I need to look into how to put them back up by technique and ritual. Something to look into.
It's a pity there isn't a Wikipedia of magical techniques...