Worried about gaining weight vent

So I’m 9 weeks 3 days and a couple days ago I told my BF I was terrified of gaining a lot of weight and getting “chunky” because he doesn’t really like thicker women.

His response to me was “then don’t get chunky”

I’m about to be 23 and it’s my second baby (his first) and I lost all my baby weight with my first, but my mother gained 100 pounds with me and never lost it, and I’m literally scared it’s going to happen and I can’t believe that was his response to me..

he’s usually so supportive and helpful and I’ve never worried about him looking for another woman, but that didn’t sit very well on my mind😔

Sorry for the venting, I don’t have friends lol