10 days is a long time, but it depends on how sick he is and whether his snot is "green" or not. Coloured snot indicates an infection, and that's pretty hard on the little bub. I have to agree with heidi that the decrease in fluids is probably of most concern, but get yourself along to a good GP just to check he doesn't have a more serious infection - he's not having a high temperature at all is he?