Babies may not belch after every single feed. Babies are burped in order to expel excess air swallowed during breastfeeding which may cause discomfort and sometimes frequent regurgitation. Thus, baby may not belch when burped if the air swallowed is not excessive. Just burp properly after each feed and if baby belches fine, if not just leave baby alone as long as baby is not in any discomfort and not regurgitating much milk