Since your son is still experiencing fast breathing despite using levosalbutamol, budesonide, and amoxicillin-clavulanate, please do not adjust his medications at home. Fast breathing in a young child requires immediate professional evaluation. I recommend taking him to his paediatrician or the nearest emergency room right away. Doctors will check his oxygen levels and chest sounds to determine if he needs supportive care, like oxygen therapy or a different treatment plan. While heading there, keep him calm and watch for signs like his chest pulling in deeply under his ribs (retractions). Avoid panic, but seek medical attention promptly.