Cat licks obsessively.

My 4 year old cat has been doing a strange behavior for the last 1.5 years. He started to lick the roof of his mouth. We thought he was grinding his teeth but he's not. I took him to the vet and got every blood test possible. And an oral exam. Everything was normal. He has a mosquito bite allergy so we thought its some kind of other allergy making his mouth itchy. I later noticed he would only do this around feeding time and he would only do it while making eye contact with me. I started to hand feed him his kibble and that would make him stop only now he will bug me every day to be hand fed. He has done this thing now every single day. So we then thought this was a mental thing. Fast forward to about a month ago he started to do it AFTER eating and the same sound would be very loud then he would vomit all his food. He was vomiting a few times a week and once he vomited water then he fainted! The vet ran all the blood tests again and all were good. I was sent to a dental specialist and his teeth were good. X-rays of chest and abdomen looked good. They said try ant acid riniditine and I did for about two weeks. While he was on the drug things only got worse. He started to burp after eating and he looked like he was tasting something in his mouth and he would swallow a lot. He would lick his lips like he was sick so they gave him antinausea meds but that just made him sleep all day. We took him off the meds but he did not stop doing the new behavior. The vet then thought he could have a stricture in his esophagus so she did a barium paste x ray series and sent it to a radiologist and they said possible inflammation of stomach, small intestine and pharynx. Maybe IBD or infection. They would give steroids if its IBS but they said if its an infection that would make things worse and they won't give him antibiotics because they don't know if its an infection. He is on a hypoallergenic diet for over 2 weeks and nothing has changed with his mouth behavior. He has vomited only once. He started to attack his tail and excessively groom since the last vet visit. It looks like he is in pain sometimes because he will sit in a ball and stare off into space. He has alway shook his head like ear problems but never an infection and he sometimes squints his left eye while he's doing the mouth behavior. I think he has been worse maybe do to stress. The vet is thinking endoscopy next, problem is its out of town about a 2 hour drive and when I took him to the dental specialist it was a 2 hour drive and we went nuts the entire way. I don't want to put him through this stress but I need to know what's wrong with him. 1. If its an infection how can he have had it for a month (that's when he got worse) and have good blood tests and no fever? 2. If it was all mental could that cause inflammation? 3. I've read that IBD cannot be seen on an X-ray so is there really any inflammation? I'm afraid it's cancer, but he's only 4. He is eating good and not lost weight. I have YouTube videos of him doing the behavior if you want to see it. Thank you.

Thank you. Can you please take a look at these videos and let me know what you think?

http://youtu.be/Hx4zwY1UkAg
Mouth licking/ air chewing

http://youtu.be/Cso31diettM
Burping and mouth tasting
20 sec into video he starts burping
55 sec starts mouth tasting

http://youtu.be/KlFIZflfoak
Mouth tasting

Hello, my cat is at the vet for observation today. When Neelix went to the vet yesterday to do another follow up I mentioned to the vet that he was doing a hair ball like coughing thing. The vet said every thing sounded good in his lungs and she did a trachea pinch test. Neelix started doing the coughing. She did it again and he coughed again. She said it was strange like he had kennel cough. My vet is in the process of referring me to an internal specialist but it is in a city thats 7 hours drive. The endoscope would be in a city thats 2.5 hours away. Well last night he did the coughing again (he will wake him self up with the cough) he calmed down after a few minutes and I tried feeding him his dry food. He would chew the kibble a bit then spit it out. He then started doing that mouth tasting behavior a lot so I gave him 1/4 10mg Pepcid a/c (I've given his this before) with some water. He then started to run all over the house like he was in pain! He was pawing at his mouth and nose and shaking his head like crazy. He was twitching all the hair and skin on his back. He stopped finally after about 1/2 hour. He came to bed with me and he only stayed in a bunny position with his paws under him. I fell asleep and woke up and he was still like that. I tried pushing him over to sleep normally and he just sat right back up again. I fell asleep again and he was still in that position. It's like he can't breathe. Now what do you think this is? I'm so worried I'm sick.
Neelix at vet office coughing
http://youtu.be/cvXwepJxoGw