When did your jeans stop fitting?

I'm 12 weeks tomorrow and finally had to start rocking the belly band today for my jeans (my work has super casual dress code). I've always been naturally thin and petite. I feel like 12 weeks is pretty good for jeans not fitting anymore, and maybe I just wear my jeans tight? Have only gained a few lbs so far, but I honestly think most of it is bloat since I keep eating like a monster but haven't pooped in days (where does it all go?!)