hi sgk, my ds2 had green poo for absolutely ages and also had probs with weight gain, mostly down to reflux. We never did really work out what the green poo was about. One of the most likely suggestions was a foremilk/hindmilk imbalance, but nothing I did really sorted it out, even feeding from the same side for many consecutive feeds. My ds1 had a cow's milk intolerance so that was one of the first things we tried (i.e. cutting it out of my diet) and it wasn't that. I always thought the green poo was a sign that stuff was going too fast through his system and he wasn't getting enough nutrition from it, but most if not all the healthcare professionals I saw dismissed the green poo with 'breastfed babies sometimes get this' (ignoring the fact that ds2 always had it).
I just wonder, with the reflux, if his doses or drugs have been changed at all since he's been home? The doses are so sensitive to weight and if hes put on about 25% of what he was in SCBU the dose of his reflux drugs should have gone up proportionately. Also, the body eventually stops responding to some drugs and you have to move on to another type for them to be still effective (my ds2 started off on ranitidine, a H2RA type drug, and moved on to Losec, a PPI drug - most sites about reflux will explain the difference between these two).
The final thing is that is he being prescribed Motilium, or another stomach emptying drug, because of the reflux? I've always been suspicious of this being prescribed to babies fed on breastmilk, as breastmilk is digested so much faster than formula anyway. I suspect the doctors may just prescribe it automatically without taking into consideration whether the baby is on bm or formula.
In other words, it might be worth a conversation with your paediatrician about whether the reflux drugs are working and are being prescribed at optimal doses.
I do hope he puts on more weight soon, sgk. Ds2 was never in NICU/SCBU (ds1 was though) but I remember a long patch when we worried a lot about his weight gain. Well done for sticking to the ebu, though. After ds1's intolerances I was determined not to give ds2 any formula and managed through all the misinformed 'advice' or cajoling from doctors, nurses, dietitians and HVs - and I'm really pleased I did so.