My baby has acid reflux and has not been feeding well- he either cries at the breast or falls asleep. He is mostly feeding for less than 5min and feeding infrequently. As such, he end up drinking only the foremilk and I noticed his poo is now green. FTM, so maybe my question may sound silly, but can I express out the foremilk until the milk is noticeable less watery/more 'white' before letting him latch to increase the chances of him drinking the hindmilk?

To add on to the mummies' comment above, you can try to tickle your baby's ear to let baby to stay more alert during breastfeeding. This trick works for both of my babies when they were young. Also, try different latching position other than side lying so baby can be more alert. To avoid vomit since your baby has a reflux issue, do burp baby half way of milk then continue latching again. Also, prop baby in an inclined position to let him/her feels more comfortable. I have a friend whose baby has very serious acid reflux and her PD advised her to feed total comfort and to mix with breastmilk. Do check with your baby's PD if necessary.