He is obviously hungry. Your baby is only 3 months old, too young to be on a strict feeding schedule as young babies will go through several growth spurts in the first year. During growth spurts they will be hungrier and needs to feed more often as this is the way their body is telling them that they need extra nutrition to grow.
Please dont't let him wait and cry out just because you want him to be in line with your schedule. He is still too young. You should be in line with his cues instead. How would you feel if you are hungry for breakfast but only gets to eat 1 hour later?