Adventures in serotonin

I am having one of those days. I could tell it was coming after a headache last night; it felt like a migraine but I could tell it wasn't. Things often seem to change after a particularly bad one, which I've read is rather common.
It went away last night but came back today and now everything just seems to be getting worse. What makes it even more difficult is that my usual defences against mood change aren't working today. A lot of the time I can make myself feel better by thinking about all the horribly shitty things in the world. Or, at least, I can make myself feel insignificant, which makes my depression seem inconsequential in comparison to what happens in the rest of the world. And then I can do something like walk down St. Clair and give change to every truly unlucky bastard I meet and not even think about the fact that they might spend it on alcohol or drugs. S. would argue that doesn't help anyone. He may have a point, but if I want to be entirely selfish I can say that it at least helps me to feel better. And to whoever I'm passing by who has their hand outstretched or a hat resting in front of where they're sitting, at least I stopped to talk to them and smile (even if I don't feel like smiling) and give them whatever I can (which is not a lot, considering my finances are rather pitiful, now and always). That has to be better than just being ignored, and having someone assume that you're a drunk or deranged or lazy.
Today, though, none of my attempts are working. I just want to make my feelings unimportant and I can't seem to do that. All I want to do is die, and I would take myself up on that offer if I didn't have to think about my mom, my dad, my brother, S., and various other people who seem to enjoy my existance.
It really pisses me off, too, that I feel like this. I had such a great week. Stayed with my parents (which made me a bit homesick at first, but I was there long enough that I remembered why I was happy to leave, too), went to a fantastic wedding (my cousin was married at the RCYC which was followed by brunch the next day), spent a great evening at Heather's, cooking, drinking, and watching Scarface ... So my feelings towards all of this are summed up by saying, "What the fuck?"
I mean, I know why, it's just frustrating that I can't do anything about it. I took a bath. I listened to happy music. I thought about all the best things, like the bike trip S. and I went on before we were together, and when I looked back at him riding behind me and smiling and I knew it was inevitable that we would end up with each other. Or this one summer at our family cottage when a group of us took a trip to visit the monastery at the other end of the lake. We drove there and back in my aunt's huge van, with my mom and my cousins and my aunt and our cottage neighbour Lee. For some reason or other we all started singing these stupid camping songs, and halfway through there was more laughing than there was singing. Even typing that now, though, is not working to make me feel better. Right now I feel like the only thing that will make it better is to crawl into bed and just sleep my current self away.