Period on the pill

Carly
So I've been on birth control for about a year now I've taken it pretty religiously.... May have been a few hours late but never missed. 
My doctor recently switched me from having my cycle every month to once every three months. So this was my fist month skipping a period. But even though I'm taking the pills I still have had dark/bloody discharge for about a week now and it about when I would have had my periods. Should I be concerned?