HELP PLEASE I CANT GET A STRAIGHT ANSWER

My periods are always on time always regular every month. This morning I had light blood on the tissue when I went to the bathroom. Check right after and there was nothing. Went to the bathroom an hour ago and there was blood and check right after and nothing. Just checked again and still nothing. I'm supposed to start my period on Monday this is abnormal for me. I had sex about 9 days ago. I took a test from the 99 cent store and it was negative... help me please idk what's going onnnn