I feel my belly is too big for 11 to 12 weeks of pregnancy. I read that if its your second pregnancy there are chances that you would show quickly but its my first.During menstruation my belly used to grow big, have back aches and under my thighs and on my hip bones would have some cramps, could this be contributing to my showing so fast?

It could just be bloating or could be twins!

A lot of this depends on the position of your uterus. If your uterus is tilted forward you will tend to show earlier. Remember, though, at 11 - 12 weeks gestation that the fetus is only about 9 centimeters long. So, you would not be showing because of fetal growth, but possibly because of fluid retention.