SO making hurtful comments

I have always been small, after having my baby my body isn't the same. I had my baby 4 weeks ago and my SO thought it would be funny to joke and say I still had a little pregnant belly still. Then when my feeling were hurt and I was ignoring him he thought he would get my attention by calling me "pregnant gut". I am completely astonished that he would say such a thing. Even if you are thinking something like that how could he not realize how hurtful that is. Honestly I felt like I looked good for just having a baby and now my confidence is completely crushed.