SO said he will ask me to go to gym after I give birth

Me and my SO are way off from having kids and all (both 20) but we were having a conversation about having future kids...

One thing that he brought up really annoyed me! He said that if he sees that I’m putting on weight after I give birth to his kids than he’ll ask me to go to the gym and slim up a bit (“look healthy” is what he said).

He laughed it off after saying that but in my mind I got so irritated. I know it’s understandable that women will put on weight after giving birth but for him to make a joke about it and say shit like that...really hurt. It’s as if he will wants me to stay looking the same (slim) forever.

Let me just put out there that we’re only in a 3 month relationship and all my friends know about him.

Mind you, I am way slimmer than him too! He’s not overweight but he’s bigger than me. I never tell him to lose weight or anything because I like him the way he is.

I’m just annoyed at the fact that he has the audacity to tell me things like he’ll tell me to loose weight after birthing his future kids but he doesn’t see me telling him to lose weight!!

Do y’all think I’m overreacting or is it understandable that I feel this way?!

I’m looking at him at a different light now. I’m feeling iffy about our relationship TBH

Any advice would be helpful thanks! :)