baby needs pacifier?

Baby at W5 begin to cluster feed from 6.30, 7.30, 8.30. However everytime she feeds she vomit. We only feed 30ml each time and continuous do so to avoid overfeeding but she continues to vomit waterfall. It seems to be hunger cue because her fist is clench, licking tongues, keep licking our clothes, wide awake. Does she wants to suckle or does she wants to eat?! Baby also have loud burps after each cluster.