My son is 16 months old. 7 days back he had fever(extreme at night and bit lighter in day) was giving him peracetamol in gap with 4 hours. Then after 5 days of this, his chest filled up with lots of mucus. At 6th day went to Dr he gave 3 syrups for consuming for 5 days as I guess, he got chest infection. Now 2 and half day passed to those syrups. His stool in diaper is totally white and greyish, which is alarming. Like he never had this type of stool since he is born. Really worried. Kindly, please tell me what's wrong with him? Is it reaction to those medicine?or something else?

Ps: it's first poop of day which turned out to be fully white and grey.