help please

hi my sister and i are huge animal lovers and we recently decided to foster a kitten that the mom stopped feeding and he was very anemic right now we think he is 3 to 4 weeks but he is not pooping so we have tried mineral oil and pydialyte but we still have no poop! we really love this little guy and he seems happy and healthy and every thing but he hasnt been pooping we got him last friday and since then he has only had 2 poops come out one of which was really hard the other was just really small is there anything else i can try to help this lil guy?