Please help

Hi i have a 1 year old cat Monty who is displaying strange behaviour.  Last year i had 2 kittens Monty and Marley but at 6 months Marley got hit by a car only about weeks after being allowed out.  The vet said Marley had died outright but that night Monty started acting strange, wouldnt eat, couldnt even stand to look at food, would gag . All week we were in and out of vets with him having his throat, windpipe and stomach looked at. He had tubes down his throat, xrays and ultra sound of stomach. Nothing was found wrong. All bloods and other tests were fine too. The only assumption after a week and £1000 vet bills was he must have seen the accident and was in trauma from it emotionally , there was no other explanation. After that week he started to eat again and was fine.  But this last weekend  he has started to display similar things with the not eating and gagging again. Been vets and nothing again in throat, or sore or anything. He is now licking food and eating a bit but still doing strange thing with his tongue like something in his mouth. Also he isnt acting same, he just wants to sleep, seems petrified of everything even us his family. Hes usually very vocal and very loving, laying on your feet and purring. But now its like he dosnt know us and runs away from me when i try to touch him .  Im desperate now to find whats wrong. Its like its a different cat. Its like ive lost my Monty. Please help, vets have no clue.

Have you changed the kibble recently? I would seek a second opinion from another vet.

We are in England and eats whiskas or felix wet food has done since we got him at 10 weeks.  Nothing has changed only that our house is having some improvemennts done to it ie bathroom and carpets. He has always been a very anxious cat and i really beleive it might be something to do with that. The only other thing i can think is its like he has altziemers or something, it really looks like that. He dosnt seem to know who we are or know to eat. Any noise hes off like a shot. Isnt purring like normal, in fact its like we have gone out and picked up a completely different cat. Its not Monty at all. I keep going vet getting charged heaps and nothing is found or they know what it is. There is nothing else i can do. Im devastated, its like im losing Marley all over again but with Monty.

Also as of today he has managedto eat about half packet of food and some biscuits. Which is great im hoping he will carry on and eat a bit more as we go on.  But his behaviour is still strange, not coming to me when i call him, when hes here he dosnt seem to know who we are. He was always very silly rolling on floor wanting his belly rubbed and tickled but now wont come near us to even stroke him. He normally greets us in morning with lots of fuss and meowing. But these last few mornings nothing just walks past us. So very strange. i even thought has he fell and hit his head or something, as we have noticed a tiny little tooth at bottom missing. The vet said hes probably just knocked it out and wasnt concerned. But maybe he has hit his head and thats why this behaviour. Its making me sick with worry