Sometimes it takes a few cycles for your periods to normal after being on the pill.
Also, some women experience a few days of spotting before their period every month.
I began having this about ten years ago, when I was 30.
Ovulation bleeding, I am convinced, is not that common (although it can happen).
Usually when I've thought I had ovulation bleeding, it really turned out to be something else (nothing serious; I am prone to benign polyps on my cervix and inside my uterus, and have had them removed several times. They are pretty common, and can cause midcycle bleeding).
If it happens next month, consult your doctor.