I use Eucerin Original Creme (comes in a tub, got it at Shopper's Drug mart for about $20). Both my girls have this problem, except they get it on their back and legs. I tried everything and only the Eucerin Creme works. It is really heavy duty, my pediatrician recommended it.

I also went off dairy to help my youngest with her skin and excessive pooping when I was breastfeeding her, that helped too.