Help! bottle feeding question

My 5 week old daughter used to get a good solid latch onto a bottle, where she held it firmly in her mouth. Now all of a sudden she barely holds onto the nipple and spits so much of it out the corners of her mouth. She also seems to be l swalloing way more air as she's instantly uncomfortable after eating even if I burp her. She already had a reflux problem so that is not new, just the way she is eating now seems to be making the reflux worse. I'm using the dr browns bottles and she never had a problem with them before, what happened?