Help please! Spotting I think?

I started birth control in October and I had had normal periods for a month. Then my glow predictied I would have my period at the begining of novemeber which is when I usually get it. But I wound up getting what I thought was my period at the end of Novemever  (I had my full period the first week of nov) I found it strange that I got two in one month but just thought it was because of my birth control. So I marked it as my period but it was so light I later figured it was just spotting. Then early dec I bled heavy only one day. No use of a tampon. Just blood in my underwear so I marked that as spotting to. WHAT IS GOING ON someone please help I'm really scared.