So I started my period a couple days ago, and I had a bit of upset stomachness and cramps, but it was OK. I woke up in the middle of the night from it, which has never happened before, but I took some ibu profen and charcoal and went back to sleep and was OK the next day. It's been a couple days later, and today I had some terribly bland food for lunch, but had to stop because I didn't feel hungry, even though my stomach was empty. I continued to feel crappy the rest of the day, and I thought it was because I'd hardly eaten — when I don't eat properly (either don't eat or eat the wrong things) on my period I start to feel terrible, cramps and upset stomach and all that — so I made some food for myself (potato) but I really didn't feel like eating it. I tried to force myself to eat, but then I was overcome with horrible nausea and spat it out and ended up throwing up twice in a row.
What could be the cause of this? I haven't eaten anything weird or potentially poisonous in the last 24 hours (hard-boiled egg, plain rice, bread), and I don't have any symptoms of the flu or something similar, so I don't understand. This makes the fourth time I've thrown up in my life — the first two being when I was little and the last being on a rocky boat — so this is totally not normal. The menstruation is probably not related (Wikipedia lists it as a potential cause of nausea though), since this has never happened before... but does anyone have any ideas on why I feel so shitty right now?
Also, I can't be pregnant — obviously, because I'm on my period, and also because I've never done anything potentially pregnancy-inducing.