hi sir, as you have mentioned you are diabetic already protected by flu vaccine
, but your symptoms strongly favour that you have contracted the infection. may be becoz of diabetes
, your immunity is low that is why the vaccine could not give you 100% protection. but at the same time it is also possible that the virus may be of different strain not covered by the vaccine. also it may be due to your vaccination
status that flu that you have is of mild variety. what ever may be the case it will take a weeks' time so just keep your self warm and hydrated, keep your sugars under control, check more frequently and eat small frequent meals. the over the counter remedies which you have taken will give you symptomatic relief you can continue with them till you feel they are doing good to you.