This sounds like your frog was shedding. The struggling to breathe - did it look like the frog was yawning? If so that's definitely shedding. You can look on YouTube for videos of it if you're not sure. Shedding is definitely normal. I do agree with taking the frog to the vet. They're trained for this stuff. Just make sure it's a vet that has treated exotic pets on a regular basis. If you don't know of one, or if you can't find one. Try calling a local pet supply store like Petco or Petsmart. They usually have a store vet that is accustomed to dealing with such pets. Good luck!