I gave birth to my second son 2 weeks ago. He was 35 weeks.
The last few days he's seemed in agony when laid down (knees drawn up, red face, crying, squirming, hiccups and vomiting) so I've been holding him upright on me.
The problem is this means he, as well as I, get very little sleep 24/7.
Today we started gaviscon but because I am breastfeeding I have to give it separately from the feed. The instructions are to give AFTER the feed but he spits it out. The only way to ensure he takes it is before a feed when he is still hungry.
I've raised the cot end to >30 degrees tilt, tried a baby rocker, used the car seat. I'm worried about using the car seat though as it restricts his airway and he slumps down. Besides, it doesn't always work.
When I feed I have to sit in a chair as I fall sleep with him on me if I try to lie in bed 
I am so exhausted I was wondering what others' experiences might be with reflux in prem babies and how people get through!