I Have A Question, My Husband Trying To Get Pregnant,

I have a question, my husband trying to get pregnant, I took a pregnancy test it was negative and I am not supposed to start my period until the 18th but started today. Well spotting. I just passed blot clot and wanted to know if this is something I should be concerns about or did I start my period or is this an early sign of pregnancy where the egg is attaching to the wall??