Moms pregnant on birth control

For any moms who got pregnant while on BC, do you know when you ovulated when you got pregnant based on DD? I'm asking because for the first time while taking BC, I had huge amount of egg white discharge but was only on CD 7 and 8. When I was actually TTC I would always typically O on CD 13-15. Of course, I wasn't on BC during those times. I ran out to get an OPK on CD 8 and it was close to being +. I've been testing everyday since and the line has gotten progressively lighter now that I'm on CD 12 (it should be getting darker in a typical situation). It's possible had I tested on CD 7 it may have been positive. I had a stomach bug last pill pack that made me vomit 3 of my pills so I know pregnancy is possible which is why I freaked out on the EWM. I'm hoping someone can shed some light!