[Coffee.]

This happens to me sometimes on my pill, and I've been on for three years as well. I wouldn't worry about it. All a "period" on your pill is breakthrough bleeding, it's not an actual ovulation cycle, and so really, it could happen at any time during the month. Some people experience spotting in midmonth. I think just something was different with your body this month, and it did it a bit different. If this continues to happen, or maybe something else happens that makes you feel nervous about your cycle, talk to a doctor, but offhand, this doesn't sound like a problem.