I have the same problem previously, but once I switched to Mamil for a week, it really works! I think because the pre-biotic in Mamil help to solve constipation problem! Better try to switch and see!
I totally agree with u, it's rather frustrating to solve their constipation problems. Worst is because they're our LO! I think u can try feeding ur LO with prunes. It works for me, so i think for ur LO shud be okay la..