Baby not eating

So my little man is 9 days old today and I have to wake him every time to eat. Even then he only stays on one boob per feeding anywhere between 7-12 minutes. Has anyone else experienced this? Last night I wanted to see how long he would go and he went almost 5 hours without eating before I woke him. He has an appointment the day after tomorrow so I’ll be able to see if he’s gaining weight but should I be concerned? Would you be waking him to feed? TIA!