4-5 week old kitten (female) peeing blood?

I rescued a (estimated) 4 week old female kitten. I have been giving it Hartz milk replacement and give it a tiny bit of Whiskas cat food twice a day (not the crunchy solid food but the wet solid food). We took it to the vet about a week ago and they gave it medicine to de-worm it but said that it was too young for shots. The kitten knows to use the litter box and does regularly. However every other day (or two) she will pee and it looks like gooey blood is coming out. When she gets this gooey blood coming out it isn't really a liquid and stays attached to her until I wipe it away. Also she starts peeing everywhere (except the litter box, which she knows to use) when the blood is there. After I wipe/pull away the blood (sometimes it doesn't come off if you just wipe) she attempts to pee and more comes out, and it practically blocks her from peeing. When this happens it normally lasts about an hour or two before it just returns to normal. Does anyone know whats going on with her? She hasn't been stepped on or injured in anyway so I don't really know whats happening.