Regarding carbon monoxide poisoning????????

I doubt it would have given you CO poisoning, but there could be a couple things to it. First, the flames consume oxygen so maybe your oxygen intake was lowered a bit. Secondly, candles can put off serious amounts of pollution. Breathing a lot of that stuff in for a long time could mess with your system and give you the headaches. Or, lastly, you could just be stressed from studying and with your exams coming up.