Thirsty and dark blood

Hello,
My fiance and I had sex about 2 weeks ago. We had used a condom so, we weren''t worried or anything. Anyway, about a week later she said that her period had started. She said that it was kind of strange though, since she had it around March 8th. We didn''t really worry about it until a couple of days later, she threw up in the morning and she said her back had hurt. At first we thought she was sick because the next day she felt fine. Since we didn''t know what was wrong, we went to the Internet and typed in some symptoms. She had told me when she had her period that week, that it was kind of brownish-black, and lighter than usual. And she said that she was feeling thirsty a lot. Anyway, we think that she is pregnant and we just want a couple of opinions. We looked up the term that she might be having. "Spotting". Like I said before, she started having spotting after the first week of sex. I don''t know if it normally happens that quickly. Her back hasn''t been hurting at all recently, and she only threw up once. She said that she feels perfectly fine now, but the "spotting" thing still has us kind of concerned. We are both adults and getting married after our college is over, but this is kind of unexpected for us. We didn''t want a child yet, but if it is a child, then it''s a blessing too. What are your thoughts? Do you think she''s pregnant or not?

Thank You