I had sex last month on 16 I took a unwanted 72 within 48 hours and than I had 2 days periods within 7 days. It was not normal in colour particularly brown in color. My usual days are 19 20,21,22on every month now I am two days late . I had done home pregnancy test 3 to 4 times it came negative . I feel perfectly fine no sign of vomiting or frequent urination or anything for that matter . My question is 1 can unwanted 72 mess up 2 and 3rd periods ? 2 can I be pregnant ? 3 what can I do next to prevent pregnancy ?