A burp sound is not important. When baby feeds along with taking in milk they also take in air. This air then needs to escape and it can happen silently as well. Just hold baby in an upright position for three to four minutes after a feed and sometimes in between a feed too if baby appears uncomfortable.

No it doesn't mean baby is not full. Burp does not happen all the time and it may be a very quiet one which we do not hear. Pls contunue to burp and keep baby upright after feeds.