Any idea what might be wrong with me?

For 2 weeks now I have noticed there's something weird going on with me. Every day between 5-7 pm I get insanely exhausted for no particular reason, no matter how good of a mood I'm in or where I am at that time. Then my head gets dizzy and I have to go lay down. I doze off for around 15-30 minutes and wake up again. I then feel like I'm about to vomit but never do. After another 15-30 minutes it stops and I'm fresh as a daisy again. Normally I'd say it's due to the lack of sleep, but I get enough sleep. 7-9 hours is usually the suggested amount of sleep people my age should get and I always do. Another guess is that I exhaust myself during the day but I don't do a whole lot, so that can't possibly be it. Last guess would be that it's what I'm eating but I've been eating the same kinds of meals for years now and it has never happened to me before. Any guesses anyone? Think I should go see my family doctor about this?