Drinking less milk at 12 weeks

My DS is 12 weeks old. Ever since the end of his last growth spurt at about 6 weeks old, he’s been drinking only about 90ml (3 oz) on average, sometimes even less when before that, he would drink 100ml already. I’m concerned because he’s getting bigger yet drinking less than he did when he was only a few weeks old.

Moreover, over the past few days, he’s been resisting sleep especially from around 3-7pm. It’s always been his witching hour but now he cries the moment we switch off the lights or pick him up to try to coax him to sleep. He’s also been waking up crying like he’s terrified shortly after we set him down in the crib to sleep. He’s always been a light sleeper but he’s never cried so badly from waking up.

I’m not sure if he’s in the middle of another growth spurt (but he should be drinking more not less right?) or if he’s teething since he’s been having quite a bit of saliva (but he isn’t 3 months yet). I’m really confused. Oh, but he still seems to be gaining weight along his curve, if my scale is correct.

Any ideas?