I'm just over 5 weeks pregnant with DC2.
With DC1 I was really sick from 6 weeks and had to tell work at 8 weeks because I was so bad. Can't really remember when I started showing but I was proud of my bump so made no attempt to hide it! 
I do know that I had a very small bump up until the day I gave birth - I think due to strong stomach muscles as I was very sporty.
Those stomach muscles have since completely disappeared
so I'm afraid that I'll start showing much earlier.
My problem is that I want to hide my pregnancy at work until about 5 months (I want a promotion and I know they would make excuses not to give it to me yet if I was pregnant). For the sickness that will be tricky but I'm most worried about the bump.
Apart from strategically placed scarves I have no idea!
Any tips?