Thanks for posting your query.
With the available described symptoms, there appears to be least possibility of heart attack
as ECG is normal. Although you are at high risk of cardiac disease as you are diabetic and you have positive family history.
You should consult with internal medicine specialist/ cardiologist and should go for thorough check up.
You should also go for stress test
and coronary angiography
for detail evaluation of your coronary arteries status.
Your blood sugar both fasting & postprandial and glycosylated hemoglobin
must be in controlled range.
There could also be possibility of cough variant asthma
and this can be confirmed by clinical examination.
Meanwhile, you should take antiplatelets for your safety.
Dr. Mayank Bhargava