I am a first time mom of a 5 week old. He tends to have fairly long nursing sessions, 30 min + on each breast. He is gaining weight and filling diapers quite nicely, so I have no concerns that he isn't getting enough. However frequently after about 15 minutes or so he will start squirming and jerking his head back without releasing his latch. Sometimes he will do this while sucking, sometimes he will just clamp down. It happens more one side than the other. My breast is quite sore from being twisted and pulled. Has anyone else experienced this?