Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your situation, and wanted to help.
I am very concerned about your lass.
In regards ***** ***** question, she isn't in an acute state of pain (like one would be if dropped or injured) but she sounds to be in distress. Her breathing tells us that getting oxygen is a struggle and that listlessness is a reflection of that as well.
Now if she is distended to the point that her lungs are not able to fully expand for her to take a normal breath, we a re in a serious state. At her age, we'd be particularly worried that this bloated belly is potentially fluid building up (if she has a heart, liver, or low blood protein issue), an enlarged organ, or a tumor.
With all this in mind, this is unfortunately a situation where there are no reliable home treatments and she needs to be seen. Since you are struggling to do so, I do want to note some databases with vets who can help you. You can check via http://www.aemv.org/vetlist.cfm. Alternatively, you can check for your local guinea pig vets (http://www.guinealynx.info/vetlist.html) or rabbit vets (http://rabbit.org/vet-listings/), as both will often see our wee pocket pets as well. Finally, as her prognosis is very guarded and we would have to be thinking about putting her down, you can ring back those vets that refused to see her and request to speak to the vet themselves. They have a duty of care to keep her from suffering and there is no reason (they have the equipment and the training) why they cannot at least put her to sleep if she is suffering severely with this.
Please take care,