Hi...Thank you for consulting in Health Care magic.
Do not use
Phenergan for a 7 weeks old child.
Cough and cold are viral 95% of the times in children. For cold you can use anti-allergics like
cetirizine and for nose block, saline nasal decongestants will do.
Paracetamol can be given in the dose of 15mg/kg/dose every 4-6th hourly, that too only if fever is more than 100F. I suggest not using combination medicines for fever, especially with Paracetamol.
For cold you can use
Cetrizine at 0.25mg/kg/dose every 12 hourly for 3 days.
For nasal block, plain saline nasal drops will do, every 4-6th hourly to relieve
nasal congestion.
Hope my answer was helpful for you. I am happy to help any time. Further clarifications and consultations on Health care magic are welcome. If you do not have any clarifications, you can close the discussion and rate the answer. Wish your kid good health.
Dr. Sumanth MBBS., DCH., DNB (Paed).,