At 4 months, there is a long wonder week, which messes a lot with sleep. Also, your baby is now older and doesn't need to feed quite as often. Their tummies can hold more and they can go longer between feeds. Their sleep is also consolidating and they drop to 2 naps and a catnap and can sleep longer in the night too! If he takes a good feed each time, he should be fine. I used to offer a bit more before the nap but that also led to snacking and more night wakings