Woke up today. I was fine. Came back from washroom and lay down to snooze a bit before getting ready for work. Suddenly, my head feels heavy and I get this mixed feeling of low blood sugar and nausea. Then I get a headache concentrated on the top of my skull. It was extremely disorienting. Felt like I would lose balance and fall over. Four hours later, it has lessened a bit but partly there. Didn't eat anything out of the ordinary. Had to force myself to break fast with a bar of 45% dark chocolate and some chia seeds dessert as the headache didn't make me want to eat or do anything at all. It's not lack of sleep coz I slept more than eight hours. Any idea what the cause could be?