First of all, I am sorry about your cat. You need to calm down, because your cat needs you to be calm.Otherwise, he feeds on your energy and could become stressed more than he is. It could be that he has a hairball inside, or that he ate something and it didn't pass through him. You say he isn't going to the litter pan- is he peeing and not pooping, or not doing either? It is also possible, that he is going *somewhere else* under the bed, behind the couch, anywhere but in the litter pan which is a common thing for cats that do not feel good.
There are a lot of things this lump could be, and x-rays are a good start, though I am surprised the vet wants to wait so long to do them. In the meantime, try and calm down. If you can get to the grocery store, go and buy a small can of canned pumpkin. Also buy some benefiber, and a small can of green beans. Look for organic catnip- the loose leaf kind, and buy a small bottle of mineral oil. These are all things that will give your kitty some fiber or a stimulant to try and let him release his stool. Now I will give you some ways to introduce this fiber to your cat and see if he will take ONE of these ways and produce results-
Also, what are you feeding him? You say you treat him like a kid, do you feed him people food, or cat food?
Feed it right out of the can. Give him about a tablespoon of it in a canned food like fancy feasts (beef or chicken not seafood) Mix the pumpkin in well with the canned food and just set it down. Most cats love canned pumpkin.
Cook the beans and mash them (without draining them) add some butter, mash again, then drain. Put a tablespoon of cooled (but not cold) green beans on a small saucer.
Take a pinch of catnip and put it in a clean jar lid, it doesn't take much, but you might have to add a bit, because a cat's first instinct is to rub on this stuff. Your goal is to see if he will eat it.
Add about a tablespoon of this to the cat's water bowl, stir it up, it will dissolve instantly and not make the water smell funny.
This one is tricky. You need a feeding syringe, and it really depends on how much your boy weighs. but you want to get the equivalent of at least a teaspoon into him. If you have a syringe, you want to press the stuff into his mouth slowly.Take your time, they don't like the taste, so I would say that you keep this one for last.
Again, you only want to do one of these for your kitty and see if it produces results. Also, while you at the grocery store, buy another litterpan. It could be that the first one caused him so much pain he is avoiding it thinking it is a cat monster. A new litter pan might do the trick-
Good luck and please let us know what the vet finds?