Please help!

I don't know where else to go, I have talked to a lactation consultant and my pediatrician and neither can really help, so I figured you ladies might be able to help me. I have a six week old baby boy and we are ebf. He used to do very well and had no issues. Now, all of a sudden in the past week he pulls of the breast after just a few swallows and cries. He will then latch again, and immediately pull off and cry. He keeps doing this until he is screaming and won't take the breast at all. He does fine with feedings all throughout the day, but starts this at around 4 P.M. and does it at every feeding until 9 P.M. when he goes to bed. Tonight, it took my husband and I almost three hours to finally quiet him down after a bf session and I had to pump and give him a bottle, which he took just fine. My husband usually gives him one bottle in the middle of the night which he never has any issues with. The pediatrician prescribed him medicine for reflux, but that doesn't seem to be working. The lactation consultant thought it might be overactive letdown, but I pump a little bit before I feed him and it doesn't change anything. I'm sorry for such a long post, but I am at my wit's end and just want my little guy to take the breast. Any advice would be so appreciated. Thank you!!