help please asap worried

I just got done with my second period this month because I missed a few which is normal if I missed some pills you get your period well I just got done on Monday and now the past couple of days I have had brown spotting usually it is just in the morning or at night. I have never had this happen before and I am not sure what it is! What could be causing this to happen? Please give me answers! Every time I google it, they always tell me pregnancy could cause it but I have no signs of pregnancy!