just read your thread now, it is so hard to know whats wrong with them when there so unsettled, but it definatley will get better, i hope it was just one bad day for you. i remember ds went through a similar thing with the nappy changes. i read somewhere that around that age they become very aware of their bodily functions and the sensations can be distressing for them. i think this is what was happening with ds it seemed everytime he did a wee or poo, passed wind or burped it would upset him. i think he didnt like the feeling of the nappy getting wet. iykwim? good thing is it passed fairly quickly, and i'm not even 100% sure thats what it was. you can drive yourself crazy wondering and trying to figure out whats wrong with them,but its just so hard to know.
i hope things are better for you, i just wanted you to know your not alone.