My Cat Has Lost Weight And Meows Like He Is Hungry Even After Eating, What Could Be Wrong?

Hi, you need to take your cat to the vet, I thought it might be thryroid, after I had his top teeth pulled $$$ I could not afford the thyroid test. But noticed that one of his lymph nodes was swollen, located beneath his jaw at the side of the throat. He had antibiotics, then went back for a check up, after a two months, it came back bigger, and my cat lost a bunch of weight, ate a lot still, but then the vet said he also had a ball size lump in his belly.  :(...
And cancer on the roof of his mouth. I have been buying him salmon, chicken, high protien canned cat food. Regular dry food is so full of carbs. Not good for cats, and I found out canned cat food is filled with a lot of water. It is really expensive, as I have a dog, who keeps eating my cats food and a few other cats as well as two toddlers and on unemployment, why am I going into that? Because I just want to let you know that it is expensive, and most of the time, my cat wont even eat all that good food unless I grind it up and force him, so take him/her to the vet.  Find out what your options are. And good luck to you and your kitty!

I'm thinking it could be the thyroid. When the thyroid is overactive a cat will do that. Before mine was diagnosed, she couldn't eat enough.
But that would have to be confirmed with a vet. He can prescribe medicine.

Take him to the vet!!!!!