1) You DO not look pregnant at all. Just IGNORE!
2) It's possible that the lady thought you're pregnant not because of your tunic, but because you've paired it with leggings and sneakers. You know how most people assume that if you see a girl in super comfy leggings & tunic with sneakers, she's probably pregnant? It's kind of like - if you're giving up on heels, you probably are preggers. Idiotic thought!!! Pay no mind to it, because that tunic looks lovely on you!
I have told this story on the forum before, but I'm guessing you probably weren't an active part of the forum then. So a lady (she lives in my bldg) once asked me in the elevator "are you pregnant, sweetie". It was hot. I was wearing a cotton peasant blouse that ballooned out and leggings. She made me so uncomfortable with that question! I gave her a weird look and asked "What makes you say that?" Now it was her turn to be uncomfortable. She couldn't outright say "because you look fat", right? I watched her squirm as she came up an answer and quite enjoyed it. Eventually she said it was because my top was ballooning over my belly and I looked tired, and I looked at her midsection (much much larger than mine) and told her - I could actually say the same thing about you! That shut her right up. No one ever asked if I was pregnant again