Dissipating period

My period in August was pretty normal, but a little lighter than usual. September, it was pretty light, compared to any other period I've ever had. October, my period was so light, it was almost nonexistent! I had a random spotting day and took a pregnancy test 2 weeks later, but it said negative. I'm not having any crazy pregnancy symptoms, even though I wish I was. Anyone have any insight or advice? I'd really appreciate anyone's help. Or should I just call my OB/GYN from now on?