Can you answer this ?

I'm not on birth control...yet! I had sex with my boyfriend and 15 mins. In the condom broke. However he immediately noticed and took action. I dont think there was ejaculate in the condom when it broke but there still can be a chance. But this was the night before I got my period. The thing that gets to me was that my period only lasted like 4-5 days. And was a smidge lighter. But what are the chances of being pregnant in this particular situation?