Worried about being Pregnant

[Novus]

I started Yaz at the beginning of May - on May 4th. During the
first four days, I was taking antibiotics. Usually my bf and I are really careful, but on the 10th day of taking the pill(May 14th), we had unprotected sex for about 10 seconds and then stopped because we got scared that I could get pregnant.

I took a pregnancy test on May 30, and it came out negative.
I started my period on the second inactive pill (about and hour
after the pregnancy test was taken), but it was heavy for only two days and then it was just a brown discharge for 3 days. I was wondering if this is normal on Yaz. I've heard that you can get your period and still be pregnant and get negative tests, so
what do you think? Should I be worried? My gyno says that I shouldn't be worried at all...

[Novus]

Is there ANY way of finding out for SURE if you're pregnant?

[Novus]

Yeah, i took another pregnancy test this morning and it came out negative again.

[aimntrev]

Since you just started the pills your period could be weird because of that. When I was on birth control my periods were always shorter and not very heavy.