Well, I'm a little confused, or maybe you are? 1) Birth control prevents ovulation *most of the time*. So, unless you are charting, how would you know you ovulated while on BC? 2) If you were charting and knew you ovulated, why on earth did you have unprotected sex?! 3)BUT you said you wouldn't mind getting pregnant, so maybe you have stopped the birth control and are trying to get back on a regular cycle?
I know tests say that they can predict pregnancy up to 4 days before your period is due, but that only works if you have an irregular cycle and a long luteal phase. Usually, if you get your period 10-14 days after ovulation, the test isn't an accurate negative until your period is a couple days late.
Anyhow, if you got your period and the test is negative, you probably aren't pregnant. However, I say "probably" because I had a full-blown 8-day period and a negative pregnancy test and when I was late the next month, I found out I had been pregnant after all, just had a weird post-conception period.