It is, in fact, not unlikely that you have caught whooping cough. Cold viruses tend to cause running noses and joint pains as well, and the fact that your symptoms worsen at night is another hint to whooping cough.
I suggest you have your blood checked for whooping cough antibodies. Antibiotics unluckily do not improve the issue but decrease the infectiousness, and I recommend them in case of positive results.
I wish you and your granddaughter the very best!
You are very welcome!
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