Rat not getting enough oxygen??

Question
Hi Sandra,
I know this is long, but i hope the details might help.
A couple months ago, my rat's fur was almost always piloerect. He seemed uncomfortable and walked very slowly. When i gave him Ibuprofen, he felt better. The vet put him on, of course, Baytril. This did help as in his fur wasn't piloerect anymore. But he did develop a pea-sized swollen lymph node on one side of his throat. I thought it might be caused by the antibiotic (though he's been on Baytril before), so i stopped it. But when the lymph node didn't go down, and the other symptoms came back, i put him back on Baytril (the off-and-on is bad, i know). The swollen lymph node hasn't gone back down; it's been 4 weeks now. It's not growing or shrinking, and he seems to have a bit of a hard time swallowing sometimes.
Now he's on Amoxycillan and Doxycycline in addition to Baytril. There is still something 'off' with him (i thought it might be Myco or a resp. infection). Being on the 3 antibiotics for 2 weeks now, he is feeling alot better than at the begining. He's more alert, wants to come out, isn't piloerect, explores a little, cleans himself. He has a great appetite, but here are his current symptoms:
-He's losing weight, getting thinner
-But, contrairily, his stomach is kind of big and round, and is not squishy (like a fat rat's stomach might be squishy)
-Labored breathing, whole sides go in and out
-But no noises at all from lungs
-Slow, lazy, deliberate walking
-He has low energy, just lays there during play-time when all the other rats and running and 'popcorning'
-His feet and tail are very pale, which i used to think was less blood flow from the possible start of hind-leg paralisis. But then a few days ago, he fell off the top of the cage, and he tried to hang on and i tried to catch him but he fell to the floor, and with the panick and his little heart beating, he got very lethargic for about 10 minutes, just laying there trying to get comfortable, breathing heavily. And then i remembered back to when he was at the vet, and got so worked up from the vet looking him over that he couldn't walk right for a while after, he'd just flop over and lay there, which i thought at the time was from stress. But now i put two and two together, and it hit me, that his white tail and feet aren't from paralisis starting, but because he's not getting enough oxygen! I felt horrible that i didn't figure it out sooner.
But now, what can i do? I'm sure what he has is treatable. But he's been on these three antibiotics that has made him feel better, but that i would've thought would've helped any reason he's not getting enough oxygen (like Myco). But there must be something else. A heart condition? What should i do?
What does the poor guy have? And what can i do?!?
He's not even one and a half year old yet, he's got more life to live, and i want him to be comfortable. I know the vet can't help anymore, so i'm alone here. Please tell me what you think it might be.
Thank you so much for your time and interest,
Joleen

Answer
Your vet needs to check his heart, yes.  My first thought was heart disease.
 Please read Sandyscrittercity.com.  This is my website.  I have a page on heart disease and also kidney disease and one about leukemia too (swollen lymph nodes, pale extremities!)  Many vets that are not tuned in as much as I am to rat health care would never even consider leukemia yet it occurs much more often than many vets imagine.  80% of the vets that treat rats only know the basics anyhow, which is where I come in.   Anyhow, look over the pages on all of these disease and let me know which most matches your boy.  He is young for this, yes, but if its congenital, its not unheard of.   Myco that is not properly treated will also do this due to lesions on the lungs, collapsed or partially collapsed lung, lung abscesses.  He would benefit from oxygen no matter what. Perhaps the vet can put him in  oxygen while he is trying to figure this out.  If you want, I can check out your vets credentials and if they are not qualified enough to see rats, I can send you to someone that knows more about them.  It seems your not confident enough in your vet as it is or you  would not have seeked out more info, or written to me.