I Haven't Had A Period Since August 20th And Tonight

I haven't had a period since August 20th and tonight I noticed a very light brown discharge. I've had slight back pain and little cramping but nothing compared to when I get normal periods. I've been very very moody and tired lately. I've felt like sick and nauseous and I guess I've had symptoms arhat could lead to pregnancy but I'm just not sure and I'm just confused to what is happening.