J.B.
Both of mine were on formula and the first didn't sleep through the night until 4 months (and I mean from 11:00pm - 6:00 or 6:30am). The youngest got up twice a night for feedings until he was around 10 months. He gradually stretched from 4am or so into the sixes, but it took a long time! I know some kids who have continued to wake at least once a night well into their first year. Every baby is different, but I don't think you're out of the norm for a 4 month old -formula or breastfed!