It might just be a brewing cold. And tiredness.
You know, we had this bug in the house a few years ago. My sister was staying here with her daughter, while my husband was away. Her daughter picked up a tummy bug. And when my gp refused to just prescribe antiemetics for me, we called out a private doctor on a home visit. He told me the following. When there is a tummy bug going it is perfectly possible to avoid being ill, even if you have the virus in your body, by avoiding ALL fatty and sugary foods. Only plain bread, ham, water etc for a few days, and you will be fine. Sugar and fat sets it off. Now, as soon as I suspect a bug, I change the diet in our house. No sweets, no treats, no cakes, crisps. Plain pasta with tomato sauce, ham sandwiches etc. So far it has worked.....
SO, CHANGE your diet NOW. No sugar, no fat, you hear me!
Let us know how you get on.