I Was Wondering On My Period, I Have Been Trying

I was wondering on my period, I have been trying to get pregnant, well just started, my period was 4 days late, on the 4th day I began to have brown spotting, then the next day I had a light period which to me is not normal because mine are usually heavy. What can that mean? Could there be a chance I can be pregnant? Also is it possible with no evaluation or tests done is it possible for a DR to diagnose me with Polycistic Ovarian Syndrome?