Biting

So this is my 3rd baby but 2nd to strictly breastfeed. And he’s 4 months old and bites me so hard when he is awake and feeding. My older baby did this towards the end of our journey and we made it to 16 months of breastfeeding. I’m not sure if he is teething or just maybe full and that’s why he bites me but I don’t want our journey to end. He was also in the NICU for 9 days before he came home after being born and had to be bottle fed when I wasn’t up there so it makes me feel like he got used to the bottle when I wasn’t there. Should I contact a lactation specialist?