Light spotting, could I be pregnant?

So I was due to get my period yesterday , I am very regular and get it every 28 days like clockwork. But I only had light spotting yesterday morning (the day I was due to get period) and then light spotting this morning. Could it be stress? could I be pregnant? Would a pregnancy test even be accurate now? We have been trying for 3 months now..just want to see what others have experienced. Thank you!