My baby is 4 months old & coos & laughs.my friends baby is 3 months and says dada and mama. is my baby not hitting his milestones?

Baby milestones: From what you describe your baby is very normal. Google baby milestones to educate yourself so you can stop worrying to much.

Milestones OK: Your baby at four months is hitting his milestones, cooing and laughing is just right for a 4 month old baby! He soon may start to babble and imitate sounds. In my 19 years of seeing pediatric patients I have never seen a 3 month old that said "mama/dada", and it would certainly not be expected! It's so difficult not to compare your baby to your friend's! Try this site to track milestones! http://www.healthychildren.org/English/ages-stages/baby/Pages/Developmental-Milestones-3-Months.aspx

You baby is fine: Your baby is just fine. Your baby is doing exactly what is expected at that age. All babies develop at different rates, so I wouldn't worry at all. Most babies will say mama and Dada between 4-9 months.