It's very unlikely for exclusive breastfed babies to have constipation.
Just the baby "feeling" movement of gas and stool which they perceive as discomfort. IT IS NOT A PROBLEM AND NO NEED FOR ANY TREATMENT OR REMEDY! Keep breastfeeding exclusively, do not give water, orange or anything. Baby will be fine.
So long as the stool is normal (soft) when eventually passed, it's okay. But if strong like that of an adult, then you need to see a paediatrician for assessment.

Your 4 months old is expected to be fed breast milk only. No orange, water etc till after 6 months.