I've been taking Yaz for 3 weeks now and suddenly my breasts are sore. The only other time in my life this has happened is when I was pregnant. I took a test to make sure, but it came up negative (WHEW!) so I'm just wondering if this is just a side effect or if birth control pills can cause a wrong answer on a pregnancy test. I'm calling my doctor to make sure, but still, this has never happened to me on any other kind of birth control, so I'm wondering if anyone has had similar reactions.