I wouldn't worry about weight gain or loss. As long as the baby is healthy that is all that matters. Have you been to your OB or MW recently?
I only ever showed out front and of course the boobs From behind I didn't look pregnant and then I would turn around and people would do a double take and say "oh, you're pregnant!" and that was right up till I gave birth.
Everyone 'carries' differently, do get checked out though if you are worried