Cat with asthma, URI, open mouth breathing

My Murphy is 7 years old. On Tuesday I noticed he was lethargic and took him to the vet. He had a fever of 103.2 and the vet said he had a little congestion in his lungs, so he gave him a shot of Convenia. His eyes were also a little bit red, but not watery. No sneezing, no nasal discharge, no coughing. He did not eat Tuesday night or all day Wednesday. Thursday he was open mouth breathing, so I took him back to the vet. He said that he had asthma (which he had a problem with once about 4 years ago and it took weeks to get him better). He still had a fever, this time 103.6. Still no sneezing or coughing, no other usual URI symptoms. The vet gave him a shot of B12, a shot of short lasting steroids (24-48hrs), and some Clavamox. I brought him home, he went to sleep, then at about midnight last night he came out from under the couch and obviously felt much better. He ate a little bit, drank, peed. He was very affectionate and wide eyed instead of droopy.
This morning he ate some more, drank, used the litterbox, scratched on the window wanting outside. Still obviously feels better. However, he got a little uppity about scratching on the window to go out (hasn't been out in days) and he started open mouth breathing again just for a few minutes. I have a humidifier going in the room he's in, which the vet said to do. Seeing him open mouth breathing again after having the steroids scared me a bit.

Has anyone had similar experiences? It worries me that he's diagnosed with URI but isn't sneezing, coughing, or having any nasal or eye discharge. My vet tested him for FIV, FeLV, and heartworms and all were negative. I'm just a worrier and totally paranoid about my babies when they are sick, so I just wanted to see if anyone here has any advice or words of wisdom.
Any tips on what to do when he's open mouth breathing, if he seems to be having a lot of trouble? I like to be prepared.

Thanks!

If he has asthma you can actually get a steroid inhaler for cats. It comes with a little mask. It sounds to me that he's having trouble breathing. That can be caused by the excitement. I would not let him out now while he's sick though. If you want to let him out I would put a harness and a long rope on him and stay outside in the yard with him holding the rope.
I'd talk to the vet about an inhaler and give that to him if he seems to have trouble breathing again if the vet thinks it's a good idea.

URI is a pretty broad term and it seems that whenever a cat has problems with their respiratory system the diagnosis is URI. With the breathing trouble and the fever it does sound like a respiratory infection. There are different kinds of URI and the one your cat has may not cause the most common symptoms of a viral URI like the runny nose and stuff like that.

If your cat has asthma then he would benefit by having a Areokat Mask to use with a inhaler. I would ask the vet about treating him for the Asthma .

I would ask about xray. Asthma should not cause fever. Oral steroids may be in order for longer use then the shot he was given. An inhaler would be good to have him on as needed.

If it is asthma oral steriods are given for around two weeks while you get used to giving the inhaler.The inhaler has to be given daily usually 1 or 2 puffs morning and evening to keep the asthma under control.. Using a inhaler is so much better for your cats health. Asthma is a life long condition ..Oral steriods should not be given long term as it causes so many other issues.
fever is not normal with just asthma.Something else must be causing the fever.