That sounds pretty normal for 1.5 months old, honestly, and the weight gain looks really good so I wouldn't worry about overfeeding. Every baby has their own appetite and some drink more than others, especially if they're having growth spurts. The fact that your baby is going 2-4 hours between feeds and gaining steadily suggests he's getting what he needs. If you're ever unsure though, might be good to check in with your PD at the next visit just to put your mind at ease.