It is quite common to have brown discharge during your period, usually because some blood can get mixed with the increased discharge and make it appear brownish. It is difficult to say why your period is different this time than it usually is. You might want to wait a day or two and see if your period comes as usual. If it doesn t you may be pregnant, and you should take a pregnancy test. At least that would explain your symptoms. however, sometimes there could be other explanations as well, but for now you should wait and see if you are pregnant. The lower back pain and changed discharge may also just be that you are going to have a heavier period than usual (possibly even due to a chemical pregnancy or a very early miscarriage), but I wouldn t worry about it yet. At this point there is nothing too unusual to worry about and you can hope for good news. I hope this was helpful, if you have any more questions, please let me know.