What Causes Vomiting With Abdominal Pain And Cramping?

I'm a 16 year old girl and just started the placebo pills of my first cycle of birth control pills. I am now puking up everything I eat and have extreme abdominal pain. I thought it was only just cramps, but the pain won't go away. And I have been having unprotected sex for about a week now. But I have been taking my pills regularly for 3 and a half weeks now. Can I be pregnant? Could this be morning sickness? I am taking loestrin birth control, by the way