My LO went through something similar. I can't quite remember at what age... all the weeks seem to have blurred, but he was over a month.
Anyway, he slept ALL day and night and I couldn't really keep him awake to eat and when he was awake he had no interest in eating. Like you, I couldn't tell if he had just got more efficient or what. Diapers looked fine. No fever. We are EBF. It was very much out of character.
I called the nurse line. The lady went through a whole list of questions and couldn't find anything actually wrong, but since he was so young and it wasn't like him, she directed me to go to urgent care.
After much consideration and reflection on his actual behavior that day and talking to MH, my mom, dad and two mommy friends I decided to wait and see how the next feeding went and go from there.
The next feeding went just like normal and from there on out. It was definitely weird. A nurse called the next morning to check in and we both just chalked it up to a growth spurt.
LOs growth spurts don't always have to be by eating like frenzied vultures. Their bodies also really do know when to eat, IMO.
How long has this been going on?
ETA. I see now that you said a "few days".
My new question. When you say he takes so little from the bottle, are the bottle fed sessions completely independent of the BF sessions? Or do you offer the breast then after you think he didn't eat enough, offer the bottle? If it's the latter, I think he's probably eating enough. But you could call a LC or get a good scale and do a weighed feeding....?