Breastfeeding on demand help!!

I'm trying to exclusively breastfeed my 7 week old on demand and am having trouble.. sometimes he is not hungry for like 4 or 5 hours!!! Should I really wait and feed him only when he is really hungry after such a long time?? My boobs get so engorged it really hard to wait till he shows hunger cues.. also, when he wakes from his nap I've been trying to feed him because that's the only time he will really drink a full boob, but is that still feeding on demand?!? Should I only feed him when he cries out for milk?? I'm finding he is never really hungry anymore and rarely shows signs of hunger and it's very frustrating because I have a huge oversupply and am getting major pain because of this. How do other moms handle this? It seems like other babies are just hungry all the time! I wish my son was like this, I have so much milk and he can't even finish one boob. So usually after 4 hours I will just offer him my boob, or after he naps, is this normal when feeding on demand or should I wait till he's like clearly hungry, like trying to find my boob or crying hard etc.