Yes, you can try to 拍痰.
But never give Chinese medicine including 開奶茶 to your baby because he is only 3 months old. His digestive system is newly developed and cannot handle it.
It can be :
- Allergy : Is your home clean enough ? Air polluted ? Air too dry ? Too cold ?
- Milk powder : Too sweet ? He may got allergy on your milk powder. Check the sugar ingredients.
- Check the color of the 痰, and probably see doc.. He may got infection.