Spotting

I had my period last month 9/5-9/11. I didn't get my period until oct 19 I had a small brownish spot. Oct 20, had no spotting and oct 21 and 22 small spots again. I took a pregnancy test oct 22 (first response) and came out negative. My husband came inside last week wednesday. I've never had spotting like this before. I only take fish oil and prenatal vitamins. What could this be?