Not eating normal and no idea why

I am hoping that someone on here might be able to help me. On Thanksgiving my 15 pound orange cat Bear started frequently urinating and over the course of a few days was diagnosed with interstitial cystitis. During this time he stopped eating normal and even though he no longer has the symptoms of interstitial cystitis, he does not want to eat. He begs for food and I put some in front of him and he just walks away. He has had an ultrasound of his bladder, kidneys, stomach, liver; blood work; tested for pancreatitis and all came back normal. He has lost weight and the vet is talking about putting in a feeding tube on Monday. I've tried all sorts of foods and that doesn't cause him to eat either. My biggest concern is that we have no idea why he's not eating normally. Has anyone else on here had a similar issue?

So frustrated and just want my baby Bear to feel better.

Oh! I understand how frustrating it must be for you. I have no experience with this but what I have read maybe that helps or maybe you have already tried that. People say try baby food. In one episode of vet on TV i saw the guy had bought in his cat who was not eating in his case it turned out to be dental issue. I am sorry I have no useful information to give. But I do understand your frustration & worry for your cat. I hope he starts eating soon. Goodluck & good wishes.

Have you have his teeth checked?  What about trying a shot of cerenia to calm any nausea or even giving Pepcid daily for awhile?  He may not be eating if his tummy is upset or if he's nauseous.