Oh how hard and heartbreaking! Your babies sound very similar to Isobelle, she is an absolute darling, so calm and happy, and since she has been on the omeprazole you would never guess there was anything wrong (except for the excessive spilling and vomiting). She has always sucked really well when breastfeeding and we have recently had her dosage reviewed. She is now on 2mls of omeprazole twice a day but maybe it needs to go up again, I will go back to the doctor and am planning to go to the Family Centre next week too.
We haven't actually had her diagnosed with a dairy intolerance I have just noticed that whenever I have any dairy that she is very unsettled, farting a lot and projectile vomiting even more than usual. I had a dairy intolerance when I was little and so did my husband so I've put two and two together. Taking dairy out of my diet does help. I tried Soy but that was even worse than cows milk and her reflux got twice as bad. I know they can do allergy tests but I've been told they don't usually like to do them on very young babies because it involves making pinpricks along their arms. Still if you are really worried about it I would ask your doctor about them
One doctor suggested that it was just wind in the intestine that was causing the hard tummy, wind and pain but after watching her and my diet I can definately see there is something else there. And we bring her up to burp every minute or two whether bfing or bottle feeding and she still has bad wind.
Isobelle does those mucosy poos as well and they are very smelly, I think it is the omeprazole and the thickened formula. Isobelle's are usually more yellow than green but there is a range of what is normal in terms of colour. My plunket nurse said that its only if it is a bright yellow or green that there is any need to worry. We supplement feed with Karicare HA AR because she spills so much and the doctors and ladies at the family centre were worried about her losing weight. Our family centre and plunket nurse said that would be the best formula if she has a dairy intolerance because it is specially designed for babies that are at a high risk of developing allergies. What formula is Jackson on?
Im not sure about whether reflux comes and goes but before Isobelle went on omeprazole she definately had times when she was worse than others. I guess it makes sense.
I expressed after her last feed (which lasted all of 2 minutes on one side) and only got 50mls total. Think the damage to my supply might have already been done.

I think I may have to consider going to formula. I went through 7 months of taking medication, lactation drops and lactation teas and expressing 3 times a day to maintain my supply with Dominic and I don't think I can face that again. It is so exhausting and time consuming. Still I was hoping to bf her for at least 6 months and at best a year.