Light spotting instead of regular period?

I normally have a regular, 5 day period, every 3 weeks. I thought my period was late by about a week, and i'm only spotting. Not enough to even call it a period. I'm 36, so the thought of pre-menopause comes to mind, but also, the last time dh and i had was about 3 weeks ago, so could this mean something else? Thanks.