Could you be pregnant if you are on birth control and you just ended your period but for the last two days you have been throwing up all night?

Or maybe it's food poisoning or a stomach virus. Take an HPT. They are far more accurate than asking this board. It is unlikely to be pregnancy. If the test is negative make sure you use an additional form of contraception for two weeks or so as the stomach upset will have reduced the absorption of your birth contol.