Pediatrician pushing sleep training

Just left our 4 month appointment and I mentioned to the pediatrician that my son was still waking 3-4 times a night to nurse/be soothed. She basically said that he needs to be sleep trained now or he will have developmental problems from not getting enough sleep. My boyfriend has been trying to get me to sleep train him too but I’m just not ready. I physically cannot hear my baby cry and not go soothe him. I feel so frustrated because now my boyfriend is calling me selfish for not being ready to do it yet.