Absent period

Sa

I’ve been on birth control since October 2017. I’ve never had any problems with it. I’ve always taken it right on time. And have never missed it. My period has always started on the Friday that I begin what I call the “period portion” of my pills. Well. No sign of my period up until this morning (Monday), however. It came and went. Also, it was the dark reddish/brown color that your blood gets at the end of your period. Literally, I spotted on 1 panty liner at 7 am, and here I am at 6 pm and haven’t bled a drop since. Of course I got spooked and got a pregnancy test. 2 tests later, both negative. What’s going on with my period? I’m not cramping or having any of my usual normal period symptoms, so at this point I’m just baffled. Any ideas? Anyone else had this problem before?