What's going on

I'm on birth control. Tri previfem. I take all my pills on time. I had my "period" (breakthrough bleed) two weeks ago. But I've started having really light spotting the past couple of days. I've been on this pill for 5 years and have NEVER had spotting inbetween "periods." It's making me a little paranoid that my birth control has failed me and I'm pregnant. I don't use other protection and haven't for 5 years. Just the pill. Is there anything else that might cause spotting like this??