Most things of relevance not mentioned 🤨.
you don’t mention age, but obviously above 20 weeks. Are they now able to sit upright or not?
this would not be new as if they are not keeping down milk it would have occurred from birth, or has it started only at a particular point?
as your baby is >20 weeks they have obviously been keeping something down as you don’t get to that point not being able to keep anything down.
what percentile are they currently?
when they went to A&E, as you were sent home with instruction for referral, I would think there was no dehydration or that would have been addressed on the spot in A&E, and condition was such that inpatient treatment was not immediately necessary?
with filming, there are two adults presumably, it would help if one filmed and one assisted the baby if necessary rather than no filming and two parents assisting baby.
understandably, this is distressing as parents, but if current condition allows (presumably if sent from A&E), your main aim should be getting into the paed asap to start hall rolling on tests required in a systematic manner.