If you're on birth control how do you know if you become pregnant?

I'm wondering what birth control you are on.If it is a birth control that you can stop taking that would be best,because it could hurt the baby.There are symptoms when you are pregnant.But it is best for you to get tested.Its best for THE BABY! A missed period would be the most obvious sign but if you suspect that you are pregnant get to your doctor asap that way you can stop your birth control and begin getting prenatal care so that you can have a healthy pregnancy and baby hope everything works out for you Good Luck and God Bless!!!