TLDR: My baby's lost 3 oz in the last three days despite feeding whenever hungry, increasing supplement, being content after feedings, having heavy wet diapers every few hours and big poops every other day (his normal), sleeping normally, etc. What is going on?
Long version: Poor weight gain at first despite working with LC to increase intake and pumping. Began supplementing with formula at 1 month and quickly started gaining. We've been supplementing ever since (and still pumping 6-7 times most days), using a Lactaid for the past few months. Supplement was steady at 12 oz per day, 3-4 of that my pumped milk, with good gain. He is 5 months old today.
Then a week ago we had almost a week with no gain and fussier behavior at the breast when I wasn't using the Lactaid (we weight him every other day). Near the end of that I had a day when my pumping output dropped, but it went back up the next. We upped the supplement from 2 oz at a time to 2.5 oz at a time and added an extra supplemented feed on the days when he ate frequently enough to fit it in. Gain picked back up, 2.4 oz in four days.
Then on Saturday my pumping output dropped again. I didn't stress too much because it had gone back up before. On Sunday it dropped even more and he ate much more frequently--9 supplemented feeds vs. 6 or 7, for a total of 21.5 oz of supplement that day (he left an ounce behind in one of them). So I was already planning to bump the supplements up to 3 ounces each for Monday, when his weigh-in on Monday morning showed a 2.8 ounce loss!
On Monday I went ahead with 3 oz supplements and he didn't need to eat quite as frequently, so he got 20 oz of supplement (again had one he didn't finish--and another time I tried to nurse him when he wasn't really hungry and he wasn't interested). My pumping output went back up again to the high side of normal for me.
This morning I weighed him again and another .3 oz loss over yesterday! What gives? Could it be scale error--it's a cheap scale but we've never had a problem with it before, it's always comparable to the one at the dr's office. I just weighed a gallon of water on it and it was correct.
Is there a chance that he is not getting enough to eat despite normal behavior and diapers? Could there be something else causing loss? What can I do to get him gaining--I am feeding him as much as he wants!