Hi Your 13 week old boy requires expert Pulmonologist & Gastroenterologist management as he has Gastro-esophageal reflux. If weight gain is sufficient & his wheezy chest episodes are not accompanied by aspiration pneumonias, then medical management with upright positioning in chair for 45mins after feeds, gastric prokinetics (like Domperidone) or thickening the feeds using corn starch or using antireflux infant formula can be tried. Depending on severity of complications secondary to reflux, like  frequent severe aspiration, even surgical procedure like Nissens fundoplication may be required!