I Have Never Missed A Period But I Didn't Have

I have never missed a period but I didn't have one in November I started my period December 4th it was a light one then I didn't start again until January 8th and it was light pink and brown only lasted 3 days I started spotting again on the 14th with abdominal pain it's January 29th and still spotting a brownish color and severe stomach and low back pain. What is going on please help