Thank you for your query on Healthcare Magic.
in a 4 months old child is a quite uncommon diagnosis.
I suggest you to go for complete investigations like CBP, Malarial parasite, blood culture
and sensitivity, CUE, after discussing with your Pediatrician
The green stools are due to antibiotic associated or due to infection in gastrointestinal tract.
You can give oral probiotic like lactobacillus
or saccharomyces with your doctor advise.
I advise you to be in regular follow up with your Pediatrician and evaluate for the focus of infection.
Hope I have answered your query.