You need to research a little more. I have a cousin who was a size 7-8 and did not show she was pregnant until her 9th month 4 times. The only way we would catch on to her being pregnant was if we was around her enough to notice her eating habits.
I Am 6 Months Pregnant And Just Found Out? Need help
Kate Smith
answered this
Cryptic Pregnancy: When You Don't Know That You Are Pregnant Until The Baby Is Nearly Due