Your child is to small for oral medication. Usually medicines for cold causes drowsy ness due to which kids drink less milk and none of the medication use mentioned are shown to be effective below 6 months and according to product monogram it’s contraindicated. Just continue saline nasal drop every 4 hourly for days. If nasal congestion is to much then you can use nasal aspirator to suck out nasal secretions.

you can  js give one drop of nasoclear in each nostril four times a day..  it will help you  But if it doesn't  then you  can just give 1 ml of drop sinarest if your baby is  3-4 kg If you  have nebuliser  at home you can js nebulise  twice a day with normal saline to get the effects.