well it is normal 2 grow but not that quick i would sugest u get checked out for preclimsia or thyrode problem they make u also put weight on very quickley just a sugestion
yeah some of my shirts that do fit show my belly now so i have been wearing long tank tops under them...
Usually between 11-13 weeks is when your uterus pops above the pubic bone. Then you start to show.
Before this it's mostly bloating. I looked pregnant very early on and at 12 weeks none of my shirts covered my belly. Just like everything else in pregnancy when you start to show is different for everyone.
I am almost 30 weeks and can still wear Pre pregnancy shirts however I am NOT the norm at all. But I have heard that the shorter your torso the more quickly your tummy will pop out. I have a very long torso so there is less popping out. As long as you aren't gaining a crazy amount of weight I wouldn't worry about it. Every belly grows at different rates and looking pregnant is pretty sweet, people offer to help carry things for you, open doors for you, give up their seat for you. I have the opposite problem, not looking obviously pregnant people give me dirty looks if I park in the expectant mother parking or if I ask for help carrying something to my car from a store. Live it up :)