Loki was hot on Friday when it was 80. Hopefully you can get your AC fixed because that will help. I have found that my pups do not do well with sudden temp changes. They do fine in 10 degree weather in February but shiver for days the first time it hits 40 in October. They do not enjoy the first few weeks of heat but slowly adapt and by August they are fine as long as we avoid the hottest part of the day. Sammy is less affected but she is not overweight like he is. A short haircut will help too! Mine get shaved next week.
We had Loki's thyroid checked and it was only like $60 so if that's what it could be, at least it isn't extremely expensive.