Hello, I would be happy to help you with your question.
The chance of pregnancy
in your case is extremely low. Also, the i-pill has the effect of delaying ovulation. Finally, it is not uncommon for women to have a small amount of breakthrough bleeding
with ovulation. So, the better explanation is that you had a delay in ovulation, breakthrough bleeding during a delayed 'mid-cycle', and will probably get your period in about 2-3 weeks. It is very important to check a pregnancy test, though, to rule out pregnancy. I would do this test in about 1-2 weeks.
I hope that this helps and good luck!