My cat has lost a lot of weight and is very lethargic
Hes been sick a couple of times
May have a tumor should take it to a VET - Asap.
you should bring him to the vet
Take the cat to the vet, something's wrong
Contact your vet.
your kitty needs to see a vet. asap!
I do agree with the above. If you love your kitty, take it to the vet.