Wow! I can say with all honesty that I know exactly what that panicky moment is like! And I agree with Britwife, get it out of the way now (or at least what you can. Trust me, your days of panicking have only just begun. There are so, so, SO many more things for you to freak out about for the rest of your life!)
Congratulations!
First thing to do is make an appointment with a doctor. Get your prenatal vitamins and quit smoking and drinking (if you indulge in either.) And get yourself a book, if you like! (A pregnancy book, I mean.)