Help! Pregnancy question!?

About two weeks ago, my girlfriend and I had protected sex. This happened during the middle of the month. A few days after we had sex, she took a pregnancy test that was negative. A few days later, she took a pregnancy test that was positive. This past weekend, she had her period on schedule, but she only had it for one day. No spotting has occurred. I am aware that the tests may be inaccurate because she took them early, before her period. What can I do? Any advice?