Birth control and Pregnancy

Hi, my girlfriend and I had had sex and for a week now she said that she has not been feeling good. At first, we thought it was because of the birth control but now she seems to think otherwise. Now, she has been on a birth control for about 3 weeks. We took two pregnancy tests, one generic and one name brand and the generic one said she wasn't and just this morning the name brand one said she was. I am praying she is not but do you think that the birth control is having an effect on the test and making it say positive or do you think she really is pregnant? Because we've been careful using condoms and birth control.
Also, she will have her period in about 6 days. If she still has her period does that lessen the chance that she really is pregnant?
Thanks, Alex.

It does lessen the chnace that she is pregnant if she does have a period.

I would reccomend having a preganncy test at planned parenthood, that way the results are read by pros.