Is My Newborn Kitten Sick?

I don't know what to do..:( one of the three newborn kittens I rescued which are now six days old..one of them is crying in pain..and is terribly weak, we are still working on trying to get it too eat..but I'm so scared that we are going to lose him.What can or should I do? Please help.

My kitten is a male of 8 days old, its constantly urinating so is always wet, down below seems very sore and a little swollen, when its mother cleans him it seems to cry in pain