Thanks for writing to health care magic.
A three month old infant can cry because of several reasons. Do not worry if the baby is other wise active playful and gaining weight normally.
may be one of the causes for excessive cry. It improves with proper burping after feeding.
Green stools are because of increased bowel movement and require no intervention. Do not worry about the green color of the stool.
We as pediatricians do not advise any gripe water to the babies. A baby of 3 months should be exclusively breast fed and should not be given any thing else
Hope this helps.