My guess would be bloat but I really cant say for sure.
When i was bloated week 5 I literally looked 5 months pregnant.
My tummy was stretched out, I felt a pulling on the top & it was just plain weird!
I couldn't zipper or button my jeans ESPECIALLY when at my desk.
I looked "inflated". It went down & Im back to normal (for now)
Everyone is different. Ive heard that if its your first baby you probably wont show until week 18 or later. Also your torso length can effect how much you show & how fast.