I have had brown spotting for the past couple of days with fatigue, backaches. What could be wrong?

That's about 2% of what a doctor (or anyone here, since this site is open to anyone to answer) would need to know. Even if we asked you 50 questions, we couldn't answer something so common and general. It could be anything from nothing to mid-period to light period to pregnancy to something wrong.

This could be anything as the previous post has already stated.. could be the start of a period,(again I'm just guessing).You need to go see your Doctor who can give a correct diagnoses.