What Causes Vaginal Spotting Along With Abdominal Cramps And Nausea?

So my period didn't come for a month, I took a pregnancy test and it came back positive. I took another one a week or two ago and it came back negative. I have felt nauseas for over a month, and looking or eating food just makes me sick. Well yesterday, i felt light headed and I got cramps but they hardly were painful and today I started spotting or my period i'm not really sure yet. So what should I do?