8 week old only taking 60ml (2oz) per feed?

El :) pregnant with my 2nd bump❤

Hi everyone! I'm after some advice and experiences! My son who is 9 weeks old on sunday will literally only take 60ml of milk per feed (bottle, Aptimal) he stops at that and falls asleep. Sometimes he will still be awake and we will burp him and offer him more but he will cry and refuse the bottle. He will take 60ml every 2-3 hours and then he sleeps from 9pm - 5am this is his own schedule! I have changed teat size, i have tried stripping him down to just his nappy to help stimulate him (it's hot in the UK) but nothing works! Sometimes he will have 60ml then sleep for an hour and take some more, maybe another 30ml but i find its a fight to get it into him, its like he cries and cries when its offered and then he will suddenly realise "oh its food!" and then drink! I'm getting lots of wet nappies, one poo per 24hrs and he is about 11.6lbs. I have spoken to the doctor and she's checked him over and says he is fine. Just wondering if anyone has experienced this and did it get better? He used to drink 120ml per feed every 4 hours.....so i do not understand why he has changed it! Thank you in advance!!