Pseudomonas is considered an opportunistic infection. It primarily settles in where something else has compromised you lungs and or sinuses.
As I mentioned above, not every doc is familiar with progressive treatment. The Gold Standard for treating these is National Jewish Health, Mayo and a few other major centers. Since your local docs have been unable to arrive at a diagnosis and effective treatment, it is certainly time to ask for a referral. With how crowded and tightly scheduled facilities are these days it may be better to have a referral than to self-refer. In what part of the country are you located.?