Can people guess you are pregnant?

Ts
I am about 7 weeks along, and lately had women guess that I am pregnant. I have no belly bump, I haven't told anyone I am pregnant, but it makes me curious whether anyone else had that happen, or whether you can guess if someone else is pregnant (without external evidence)? Is there some sort of "glow" that we have? Or maybe I just look desperately bloated? Haha.