Pregnancy

Last weekend I unprotected sex with the guy I am seeing. We had sex four times and two of the times he didn’t pull out. I am on birth control but the child I do have, I got pregnant with while on bc. I took my pill late the night before and the night of us having sex. The next day after he left, I started having breakthrough bleeding due to taking my pill late.

I was just wondering what the chance of pregnancy might be?