Actually a lot of women have brown discharge prior to their period and directly after and it's completely normal. Wait to see if your period shows up, if it doesn't or continues to be weird and mainly spotting or shorter than usual, take a test. You can go ahead and test now though as it has been 2.5 weeks. If you are too young to be pregnant, then you really need to invest in birth control. Your old enough to buy condoms. You can get on the pill. Or stop having sex. :>) Said with kindness because you are absolutely right, an unplanned pregnancy can change the trajectory of your life and often not in a positive way for a young woman with many goals for her future. So, after this, always use protection (pull out method does NOT prevent pregnancy either, has to be condoms or the pill). Anyway, you hopefully dodged a bullet. Take a test and find out if your period doesn't show up. good luck