Oh wow how much did the second weight in at.
I'm definitely showing sooner with the second. At 6 weeks, I started to wear my looser clothes. At work, I only zip my pencil skirts half way. I'm in week 10 now, and my pants no longer fit comfortably. And I've only gained 3 lbs. Just think about it this way... It's easier to blow up a balloon that was previously inflated/stretched than a brand new balloon ☺
But you'll be told over and over that each woman is different just like each pregnancy is different. This proved true for me. During my first, I loved the support and security pants and skirts with belly panels provided. I even wore preganacy Spanx. I was excited to be able to wear my matetnity stuff again this time around but when I put them on...this second baby tells me he/she doesn't like being constricted at all. Everything has to be loose and under the bump. No belly panels! So I already have to buy new maternity clothes at 10 weeks because I'm showing earlier and I can't wear a lot of my old stuff.
I was showing enough for my husband and myself to notice at 13 weeks. This is my fifth pregnancy but only the second one to make it out of the first trimester... but as mentioned above every pregnancy and every body is different, so YMMV.
Impossible to answer really,everyone is different
I barely showed with my second i was eight months and people assumed i was only 6. Different everytime