[18M] I occasionally go overboard with joking around with my girlfriend (18F) and I'm looking for some advice on how to rein it in. Any tips?

I've been dating my girlfriend for nearly six months, and things have been really great between us. We have a lot of fun together, always joking around and laughing. However, about two weeks ago, I made a comment after she got a large cookie at a restaurant—just a light-hearted “Well damn”—and it unexpectedly upset her. She started crying and later opened up about feeling insecure about her weight. I reassured her, emphasizing that she looks amazing and that I love her for who she is, not for her appearance. I apologized and promised to be more careful about joking about her weight. I felt terrible afterward because I never want to hurt her; I want to be someone who lifts her up. But just a few days ago, I made another joke about the same topic, and she ended up crying again. I apologized once more and committed to stopping. I realize that I tend to get carried away and say things without thinking first, and it really bothers me that I might be making her feel bad about herself when I truly care for her. I’d appreciate any advice on how to stay mindful in the moment and avoid making comments like that in the future.