What Causes Only Spotting During Period?

Hello,I have been experiencing some old blood spotting... not sure a better way to explain it. Basically my menstrual Cycle is about to start, and instead of getting my normal monthly visits I'm getting old blood and its only here an there in small spots... basically not even enough to use a tampon or pad. I've never had an issue with my period before, its always been a regular flow and its always continued 4 days with a 32 day laps in between periods. My Husband and I are trying to have a baby... and i've read a few articles that have said that this could be my problem... that I'm starting to have a baby, im just a little scared that my menstrual cycle is off... do you have any answers for me?