My 5 year old chihuahua is really struggling to breath.

Question
I have a 5 year old chihuahua and for the past few months he has really been struggling to breath and it almost sounds like he is congested. I have took him to the vet numerous times and they can't seem to figure out what is wrong with him they've done everything from blood work x-rays and steroid shots thinking it might be asthma. But the blood work and chest x-ray were all good. His breathing gets really bad when he gets excited but it never really gets better. When he lays down and relaxes it seems to calm down a little bit but he still struggles. We've found that when there is a little pressure applied to his rib cage it the only time he can really breath right. I really just need to know what you think might be wrong. My dog eats healthy and lives in a very clean environment. Please help me.

Answer
Paula,
What did the xrays show? Was he checked for a collapsing trachea? This is a common finding in little dogs and especially Chihuahuas. Does he cough when he gets excited? Is this something new or has he had it all his life?
I am not a vet but he could have a pleural problem, that is, maybe it's not in his lungs but around his lungs. Is he on heartworm prevention?
He could have pulmonary heartworms that are not going to show up on an xray.
You need to take these questions to your vet and see what he says about them. If you cannot get any answers then consult a pulmonary vet. This could also be a heart condition. I would have a veterinary cardiologist look him over.

I hope you can find some answers soon.
Let me know what you find out.