4 week old suddenly clusterfeeding

My baby is 4 weeks old and we had a bit of a rough start breastfeeding. I exclusively pumped and bottle fed for the first 3 weeks but had been trying to get him to latch daily and out of the blue last week he latched and has successfully been breastfeeding ever since. That was a huge relief but in the past 24 hrs he has seemed less content and has been clusterfeeding every hour, even overnight where previously he was content to go 2-3 hrs between feeds. He is also arching his back away from the breast every so often like his stomach is bothering him. He will also make gagging noises when laid flat on his back after eating. I should mention that he had reflux like symptoms the first week which led to our lactation consultant recommending we feed him upright, keep him upright 15 mins after feeding and I cut out dairy. I am still doing all of these things. We have an appt with our lactation consultant tomorrow but I am concerned and wanted to get some opinions in the meantime.