I think she meant every 3-4 hours as that is what was said in an earlier post. Every 45 minutes would be a bit often.Every 3/4 hours seems too frequent to me. Is his crop getting completely emptied at least once a day? If not there may be a crop problem like sour or impacted crop. This is above my experience, but that is going around in my head and keeping me awake as both could cause malnutrition.
Also the amount he's being fed. How many mls is he taking? Babies eat a lot more in one session than an adult as growing takes a lot of energy. Bang goes tonight's sleep