My 4 year old has been having trouble breathing for a month. He complains of headaches sometimes but the main symptom is his breathing

.....he just keeps taking a very deep breath, then stops breathing and follows with another deep breath.

He has a hard time talking because he gets short of breath. None of the doctors he has seen thinks it is asthma or allergies.

He has seen a cardiologist and an ENT to no avail, their tests were normal. They have done X-rays, an EKG, and various blood testing but have come up with nothing. He is also type 1 diabetic and ketoacidosis is negative. He has had some problems with constipation as well and takes benefiber.

The dr tried singulair and claritin, but nothing is helping. He does not have any wheezing or cough, just the shortness of breath.

I don't know if it is pulmonary, gastric, or neurologic problem. The dr will not refer him to another specialist and says to "ignore" that he has breathing difficulty!