Sounds like my Rambo. He's 4 mos. and weighs 2lbs 9 oz as of today. I brought him to the vet for his final round of shots and she says it sounds like he has sinusitis. He sneezes and also reverse sneezes and I thought he had kennel cough, but the vet says kennel cough only lasts for 3 weeks at the most. She prescribed Chlortripolon (which is an antihistamine) from the drug store in 4 mg tablets, cut in half and given in the morn and evening. I've tried just about everything. He's already had surgery to remove parts of a pacifier.