As your problem of having cough
is since long, it can not be simply viral infection.
There might be having some bacterial infection as well and to get relief, you might require antibiotic medicine course.
It is better now to go for,
Complete blood checking,X-ray chest.
After report consult your doctor.
I hope with antibiotic medicine you will be alright.
avoid fried and junk food.
Meanwhile continue with cough suppressant syrup.
Take plenty of water and liquids to prevent dehydration
Ok and take care.