Ok, that definitely sounds like an RI though.
Is this a reptile vet? If not, many vets just haven't a clue about how to care or treat reptiles.
Antibiotics would only treat a RI if it was a bacterial infection. If the RI is caused by a virus, antibiotics will provide no help.
Lets go over your husbandry in more detail first so we can get that all squared away.
What are you using to measure your temperatures with?
Typically, the kits that you buy from stores are junk. You need to have a basking bulb that produces the proper temperatures, and a
UVB bulb. The compact/coil UVB bulbs (the ones that screw into a standard bulb socket) are not suitable really for dragons. You need the long tube fluorescent type. The ones that are able to span half to 2/3rds of your tank.
Allow improper UV wouldn't have caused a RI, it's still an important part of their health that is worth taking care of.
Can you post a picture of your tank, and of your dragon?
When you see him sleeping upright like that, in this case it will be good to reposition him so his head is angled downwards. Babies often sleep pressed up against the glass like that. And that is ok, it's perfectly normal. But when there is an RI present, you want the head angled down to help drain the lungs.
Another important thing to be aware of during a RI (and any sickness really) is to try to keep the tank a bit warmer overnight. Aim for 80 degrees. This keeps the immune system more active, and helps to dry the lungs. You will want a CHE to achieve this, no other lights as they need complete darkness to sleep well.
-Brandon