Paranoid Beyond Belief

Ever since October I've been paranoid that I'm pregnant. At the beginning of that month when I started my new pack of BC, I accidentally took two placebo pills instead of the active ones. When I realized, I took all 3 of the pills (the two I missed and the one for the current day). I had PROTECTED sex like 4 times that month and had a few dizzy spells and threw up once. I have not missed a period and even took a test that came out negative. I have no symptoms whatsoever and I continue to take my BC at the same time daily. For a while I had gotten the thoughts out of my head that I was pregnant but I just recently heard a story of a girl who was 8 months pregnant with no symptoms who continued to have a normal cycle up until she gave birth. She literally went to the hospital with "kidney stones" and had a baby 10 minutes later. Any thoughts about my situation? I'm so scared. I'm in nursing school and I literally can't be pregnant. Help. Help. Help.