I have been told by my ob that the more pgs you have the faster you show. The body can "remember" the shape and sizes you have been in the past and can expand to those sizes easier each time so even thow you may not bet bigger with baby number 4 than baby number one you may get to that size faster.
You can this is my 3rd and the dr told me I would show way sooner then the average person wasn't overweight to begin with I'm 11 weeks tues and I already have me a belly!
My tummy would go hard, then soft and kept changing. You wouldn't be "showing" yet. baby is teeny tiny atm, but you are probably bloated like most women do with the start of pregnancy or when they get their periods.
Could be bloating ... I look about 4 months pregnant in my early weeks due to bloating