Have you considered pumping and adding formula to supplement? Is he on acid reflux stuff? That makes the enzymes more effective. Also, I'd note that given his bout with constipation which gave him several days of low intake, his weight gain is good, if the doctors make an issue. Or just listen, nod and then keep feeding following his cue. Or better yet ask in your sweetest naive voice, "don't you think given our family size and that our other 9 children were always on the 20-30% growth curve that this is his natural weight?" And when they come back with the 50% blah, blah, blah, repeat sweet naive voice with "hmm, well how do you suggest we try to force DS to eat more?" Augh. Hang in there. Also, fyi: Our son's weight was like 13%ish percent first appointment and low for first year and is at 50% now. And it only drops when his tummy is backed-up for most of the time between weigh-ins.