I had sex on my first day of period, my boyfriend was wearing a condom but he didn't pull out before ejaculation. There was no leak in the condom. What are the chances of me getting pregnant?

You had sex... therefore there is ALWAYS a possibility of getting pregnant... what varies is what are the odds.

When you start menstruating, that is the time the egg is leaving its nest because it wasn't fertilized in situ, it is being expelled and after your period is over, the cycle starts over again and another egg is released for your Fallopian tube. So... I think your chances are like 25 per for pregnancy.