You need to go with your gut. If you feel you need to see a specialist then do it. If your gp won't do it, go to another to get the referral. He may just be having a bad run, but it could be linked to asthma. A friend of mines child got bronchiolitis over and over, to find out he had asthma. That may not be the case for your son, but like I said, go with your instincts.