Found stray kitten, bloated stomach and bony, also not playful.. need immediate help, she's up for adoption?

I found a stray kitten on the street yesterday. He is an orphan, I am 100% sure. He is bony and his stomach appears bloated. When I picked him up off the street, he was aggressive and bit and scratched for his life, but I managed to carry him home. He is now in my room and continues to hide in every imaginable space here. I have no other room for him, so keeping him elsewhere is not an option. However, this kitten was so aggressive when I first met him. Now, he allows people to pick him up and pet him, but he doesn't seem to enjoy it. He just sits down while being held and tolerates the petting and talking. As soon as he is put down, he sneaks slowly off before dashing for a hiding place. He is so different than any other cat; he hasn't meowed once, he doesn't show affection, he doesn't show signs of wanting food/begging for food (but he does eat, he just won't meow or come out for it), and he doesn't play. He absolutely will not play with any cat toy or any string or anything for that matter, even if it smells of tuna or some other treat. He will stare at the object and then look away, unconcerned. I have a bad feeling that there is something wrong with this 5-7 week old kitten, because of his attitude and his bloated belly and bony frame. All help would be appreciated, as I need to have this cat adopted out and I don't plan to give away a sick cat.