U child is absolutely normal as from your history and image.Growth and development parametrs are within normal for age..Neck issue which you r saying is also normal at this age.weight of baby is also normal.. continue breast feed till 6months of age and then start complimentary feed along with breast feed.
Next Steps
keep watch on weight and development parameters
Health Tips
always consult pedritician whenever you feel any issues in future.never self medicate.