u should just take it to a vet
seeing a vet only cost about 2xx dollars, they will know what to do
and if testing pbfd from the vet is too expensive
there are places that you can send in the blood smaple and it only cost about 2xx
there aren't much we can help you with if the bird is so serious
and pbfd can spread to other birds and the house would have the virus years after your bird die (if it did)
and your house would not be suitable to keep birds for quite awhile
so u have to get it check if u have other birds at home or you want to keep birds in the future