Tips for more productive breast feeding sessions

My 3 week old is still struggling with breast feeding despite numerous lactation consult visits. It seems we take one step forward and two steps back. We’ve used the nipple shield and that’s helped his latch a lot but this week our challenge has been a productive session, esp in middle of the night. He’s on each breast for over 30 min and I constantly have to express and massage the milk into his mouth to get him to swallow. He gets frustrated and I get frustrated. When I take him off for a break or burp he wants to go back on so I know he’s still hungry. Does anyone have similar experience and tips to help make the feeding more productive and not as long? Thanks in advance.