EMERGENCY--weight and appetite loss

Question
Here's the story: My rat broke his ankle a month ago. I'm not sure if it's relevent to what's happening now. He was separated from my other rats and put on a diet since he was pretty overweight. When I reintroduced him, I continued to separate him for feedings since he's a total glutton. I just stopped his metacam a couple days ago and noticed that he wasn't as hungry. Today he won't really eat at all. I've been putting bread and juice in my mouth and then spitting it into his so he has to eat. I already spent about $300 when he broke his ankle and I can't afford more vet visits.

So, basically symptoms are weight/appetite and energy loss. He doesn't seem too dehydrated but his skin is a bit paler than before. He started losing hair on his chest when his ankle was healing but I didn't pay much attention since he was otherwise fine. He seems to maybe be panting. He was also on antibiotics (for upper respiratory) about a month ago so I'd be surprized if he had an upper resp infection. He's only a bit over a year old. Any ideas, speculation or advice would be much appreciated. Thank you.

Answer
I dont think you need to really put the bread and juice in your mouth and feed your rat that way. Perhaps offer him some baby foods that are stage 1, this way he is getting nutrition and fluids at the same time, and not the pathogens from  your mouth too.

As for the fact he was on antibiotics a month ago, this doesnt mean he doesnt have another respiratory infection. Depending on how long of a duration he was on the antibiotics the first time plus the type of antibiotics he was on along with  the organism he had means alot.  He could have had mycoplasmsos last month that was causing a respiratory infection and it was not treated long enough (4 to 6 weeks) and the drug(s) of choice are baytril, doxycycline or zithromax and doxycycline.  If he has a secondary infection now, the bacteria may be resistant  to the antibiotics he was on last month.  He may also have lung scarring from last months respiratory infection, esp if it was myco.  Also, panting could mean he now has a lower respiratory infection, possibly pneumonia.  You do not always need to hear wheezing and congestion with pneumonia. The panting, weight loss and loss of appetite are three big key indicators of infection, namely lower respiratory.
The panting tells me he is short of breath so this really means he could have some lung problems. This will absolutely cause weight loss and anorexia.  Please let me know what he was on last month so I can tell what he needs now to recover. You should not have to bring him to the vets again if you have an established relationship with the vet. He should be more than willing to refill the prescription from last month if it is the  drug he needs more of now.