Baby feeding less. Treatment for this?

My baby is 3 months old. Since last 3 weeks, he is not taking feed properly. His intake has reduced and refuses bottle feed, katori chamach, and sometimes breast milk also. He is mainly on formula feed. We have changed nipples, bottles, formula but there is no improvement. Doctor gave neopeptine drops and the course completed but still he is not taking feed. It seems he is not having hunger. I offer him bottle while sleeping and he dreamfeed sometimes, sometimes not. He passes stool once in 4days since birth and color is greenish. Out of curiosity and anxiety, we did stool test and pus cells counts came 15-20 hpf. Does that mean he has infection and that is why he is not having the feed properly?? What should be the appropriate treatment for this?