Call your OB/gyn and make an appt. today. Ask to speak to the nurse, and ask her what you should do about the Xanax. I am pretty sure it is going to have a Class C rating (or unknown, thus contraindicated), for tetragenics....drugs that can harm a developing fetus. The first trimester is the most critical time in the development of the embryo and then fetus....you don't want to take any chances now.
Go and buy a home pregnancy test. I can tell you from experience though that being two weeks late is almost surely a sign that you are pregnant. So don't put off finding out about the drug, take your folic acid, and don't drink any alcohol.
Being a good mother begins in pregnancy.
Congratulations, BTW!
Jen