Is it Thyroid or something more?

My 14 year old little Tuxedo cat has some thyroid issues. she's been getting two clicks of a pen containing Methimazole ( i think, it says so on the label and i can't find her little bill that tells what the other is) she was doing fine for the good part of the year until she started to show signs of a groggy voice, which we laughed at, at first.

in the past two weeks, it's gone from groggy to gone. She wheezes when she purrs and ends up gagging herself, she whistles when she breaths and it seems like she's having a hard time in general with her throat. We took her to the vet and they did some blood tests and checked her throat. the cat came back agitated, hissing and spitting at anyone who went to pick her up to touch her. and her left side of her face was slightly puffy. we went back again. The doctor put her on an antibiotic, Clavamox. she vomits after she gets this, about maybe an hour after. sometimes it's white, and sometimes it's all bile. she hasn't touched her food that much and her stool is very soft, when she has a movement. 

The vet said her blood tests have come back clean and she's healthy in that sense, but what is going on? Her voice hasn't gotten better, she still wheezes, she still gags when she purrs and now she's not even bringing up food when she vomits.

I've had this cat since before i was in kindergarten. she's part of the family. we are all very worried about her. Can someone help please?

We can't diagnose what the issue is with her missing voice, but I can tell you that whenever I used to give my Sven Clavamox, he would also throw up froth, and completely lose his appetite and in general, act like he was dying.  Last time he was on it we said "never again". 

I would contact the Vet and ask for a different antibiotic, and ask them what could be causing the swelling on her face, and the loss of her voice.  Ask if it could be related to her thyroid.  I'm guessing if all her numbers came back normal, that it's probably not that, although was her reaction at the Vet a normal one?  (the agitation?)

Do they think maybe she is getting asthma or anything?  (just throwing things out there

)

well, she's very good with the vet, nervous, but good. never bit or scratched. we think the vet techs might have hurt her before when they were talking blood. the swelling went down, but she was still mad at us. so we think they were a little rough on her, which is understandable if they are new.

 She's almost done with the antibiotics, and we don't want to give her more after all this. she still gags herself, and threw up a little food last time... so she's somewhat eating... but now when she vomits, it's to the point where she has nothing left and is just bringing up spit.

We'll call the vet tomorrow. we know she has overactive thyroid, and we know something is in her throat, be it the thyroid swollen or the tonsils. we don't think it's cancer, although a growth ( so the vet says) is what causes thyroid issues in the start. 

I'm not sure of it's asthma... she doesn't cough at all and she doesn't sneeze. it's just wheezing and gagging, like something is there.

thank you for your help though! 

it's super stressful when we don't know what's wrong with her!