Am i pregnant?

I took a test the day my period was supposed to come the test look like it said positive but the line was really light , I am 3 days late and my period only last for 3-4 days and when I went to the ER they said my test came back negative, now I am confused because I am spottin after being 3days late but the spotting Is very light and I can only see it when I wipe , I don't have to wear a pad or tampon . Can someone please help me or tell me what could be goin on ???