It is very normal for BG to creep up when ill.
There are many things which affect BG including food, alcohol, time of day, year, month, weather, stress, illness, exercise, drugs, ...
When we are ill, our livers release sugar to help fight the bugs. For someone without diabetes, they will produce more insulin to convert this sugar into bug-fighting energy. When we have diabetes this is not so easy.
As I have type 1, I treat my high BG with extra insulin. When I am ill, I test more often and adjust my insulin dose accordingly. It is not unusual for me to need 40% more insulin when I am feeling poorly.
I hope you are feeling better soon. In the meantime, look after yourself and don't get too stressed.