2 week old breastfeeding

Angeline
Hello ladies, I'm a FTM and started breast feeding my 2 week old from day one. As of a few days ago he has been slapping my breast, vigorously latching on and off and then finally settling down and breast feeding. Sometimes I'll change position and try to burp him but he gets angry and then eventually slides down to my breast. What does this all mean? I thought maybe it meant to change breasts because he emptied it but he will do this even when the breast is full. Also, how do you know when he has emptied a breast?