my cat is behaving strange lately. hasn't really been himself lately. all he does now is sleep, sleep and more sleep. and has been really restless and lethargic looking. anybody might know what's wrong with him? or is he just plain lazy and sleepy? ive got 3 other female cats at home too and he is the last to join in the family. he used to be chasing them around the house. now, he just SLEEPS. please advice!