Have you considered switching to nutramigen? DS had horrible reflux and constipation, he would only go 1 time a week, and his ped thought maybe a milk allergy, so we used the hypoallergenic formula. It gives a bf style poo and fixed all of our problems. We noticed a difference in 2 days and had a completely new baby in a week. It was a miracle! He's now 4 and after allergy testing, he is allergic to wheat and sensitive to milk. He had a reaction, but not severe enough to be considered an allergy. We are now able to cook with milk and he eats cheese and yogurt in moderation, but still primarily use almond milk. It may be something worth talking to your ped about or just trying a couple of days worth to see if it helps.
It is very expensive and smells funny, but dh and I got over that as soon as we saw the difference. And our ped was really good about stocking us with lots of samples at every appointment!
Sorry if I haven't gotten back with anyone via PM. Still learning the iPhone app and not very "techy".