Spotting and a late period

So my last period was about a month late for some reason(i'm guessing stress) and today I noticed some spotting when I went to the bathroom. I'm not on birth control, and I haven't had sex in over two years, so I'm not concerned that it's a pregnancy. I was wondering if anyone had any idea as to what might be the cause? I will definitely be going to the doctor, but do you think I should be worried?