Help! Really uncomfortable hairball? Or something more serious?

My cat Karma (3 years old) is usually very outgoing and active, but yesterday her behavior completely changed. She just sat on the floor, very lethargic, with her eyes half-closed, and her mouth slightly open. She didn't seem interested in affection or petting, and when she did decide to move, she did so slowly. Every so often, she would make a gagging/hacking motion, but there was no sound and nothing came up.

I thought she might have something stuck in her throat, so I took her to the vet to have her looked at. At the vet, she acted pretty normal and didn't act lethargic or strange at all (probably being stressed about the strange surroundings/people). And when I told the vet about her symptoms, she felt various places around her body and seemed to think that it was probably just a hairball. Because the vet was concerned about Karma breathing with her mouth open, she took an x-ray to see if it was asthma, which it apparently wasn't. She gave me some Laxatone lubricant to feed her to help her pass any hairballs. So, I came home fairly confident that she would be fine, and that there was nothing to worry about.

However, after we got home, she started acting the same way, and has been doing so all yesterday afternoon/evening and this morning. She just sits in one spot with her eyes half closed, and looks uncomfortable. Normally, when she's relaxing, she'll sprawl out on her side, but now she doesn't seem to deviate from the 'head-up-while-dozing' pose. Every so often, she walks around, but doesn't seem very happy about it. She is eating, but doesn't seem interested in drinking (and because I'm paranoid about her getting dehydrated, I've been spooning a little water into her mouth every so often. She's had two doses of the Laxatone so far, but isn't making any progress at coughing anything up, and doesn't seem to be hacking as much as she just sits there, not wanting any attention. This is completely different from her normal energetic and affectionate behavior.

Does this sound like normal hairball behavior? Is it just a particularly uncomfortable or hard-to-pass one? Should I keep giving her the Laxatone, and see if anything happens? I've never had a cat with hairballs, so I don't know what is/isn't normal.

How would it be possible for her to be eating with such a big hairball stuck in her stomach or throat?

Does this sound serious? Does anyone have any ideas as to what else it could be? Should I take her back to the vet?

I would say Asthma but the vet said it isnt Asthma.
I would call the vet again and take her back though and try to find out what is going on.

Time for another trip to the vet and/or a second opinion. Something's definitely wrong with your baby. The open mouth breathing and lethargy are a great concern to me.

I would definitely take her back to the vet and have them do an ultra-sound. The ultra-sound will show things that the X-ray didn't. An ultra-sound is also what detected my Samson's hepatitic pancreatic issue

That is true ultrasounds help. Coco has had them before.

Well, I took her back to the vet, who checked her out and still seemed to think that she was going to be fine. Apparently she had a lot of trapped gas, which was probably due to her trying to pass the hairball as it was moving slowly through her intestine. The vet gave her a steroid injection to help with pain or any inflammation, and this seemed to make her feel lots better. As soon as we got home, she had her energy back. I've continued giving her the Laxatone, so if she hasn't passed it yet, hopefully she will soon. Until then, I'm just keeping watch for any more symptoms. The vet said that if she failed to improve, the next step would be an abdominal x-ray or ultrasound-- but that as long as she's eating and doesn't have vomiting or diarrhea, things should be looking up.

Thank you everyone for your input!

Did she give her anything to help with the gas? Sounds weird that a hairball would cause this problem. You can also give her a bit of pumpkin (plain canned, not pumpkin pie filling.) to help her pass those hairballs.

Stephanie