So I went into the doctor's office again today (this time with my Mom) and we came up with some answers (not that I'm being generous with the term answers).
The Doc still doesn't know exactly what's wrong with me, but he and my mom both agreed that I should get on some pill to knock my hormones into some sort of order. Any men-folk reading this post might not want to read from here down. You've been warned. The next 'safe read' zone will start in bold.
They put me on birth control pills. Which is weird to me because I'm 17 and nowhere near sexually active. But I've always had an irregular period, and since I started running, I haven't had one at all. While the doc claims that this isn't unheard of, he feels that it might be a good idea to force my cycle into action (through the pills).
I could care less whether or not I get my period as long as my energy picks back up and my insane mood swings settle down to normal PMS mood swings.
Men-folk can pick back up here. The aforementioned problem, however, doesn't seem to explain my weight gain. The doc, my mom, and the nurses swear up and down that the weight gain isn't a problem and that it's probably just muscle. I'm not fully buying that. The doc said it couldn't hurt to watch my carb intake (since I'm vegetarian, he thinks I might be replacing protein with too many carbs) so I'm going to try that for a little while and see if it doesn't get me anywhere.
Until then, I'll just hope that this new 'solution' will pick my energy back up.