Any ideas how to gt a 7 month old kitten stronger. He's had tough going the last couple of months but seems to be improving now. He just isn't very strong. He can't jump up on anything. He doesn't clean himself. He stinks. He doesn't cover anything in the litter box. He stays in an upstairs bedroom overnite and has no problem climbing down the stairs in the morning. He's quite small. More like a 3-4 month old. Only weighs 3 lbs. He eats pretty good and drinks plenty of water. Any suggestions? He eats both dry and wet food. But not a real lot.