What Causes Spotting Instead Of Periods?

I am an every 28 day cycle person. I was a day late then all I did was spot and and for a couple hours had a very light period. Bright red blood watery then lots of clear mucus. No clots which is unusual for me. Usually my blood is thick and brown. Having pregnancy symptoms. Then I stopped spotting for about 20 hrs then started again for about an hour. Then did that again the next day. I just started charting BBT and it is still dropping. My husband and I have been trying to concieve for 1 1/2 years. Any idea what might be going on.