Feel like baby isn’t eating enough

My baby is on formula. He is 3 months old and lately he’s started only wanting to take 2 oz at some feedings . He turns his head and hits the bottle after taking one sip . I try again and the same thing . Sometimes I can get him to take 3 oz and then about once a night he will surprise me and take 5 oz. according to daycare he eats good (usually between (3oz-6oz) every 3 hours ..roughly 2 to 3 times while he’s there . We usually have our last feeding of the night around 9:30 or 10 and I put him to bed. He’s been waking up at 1am for a feeding and does pretty well, then at 5 am he wakes up again and doesn’t eat that well. He doesn’t have another pediatrician appt until the middle of next month . I’m just worried that he isn’t getting enough to eat . He was over 13 lbs last month when we went to the Dr , but I’m not sure what he weighs now. I’m wondering if I should stretch his feedings to every 4 hours or what. He’s just getting difficult to feed.