I Had Sex A Few Days Before My Birthday June

I had sex a few days before my birthday June 8 with my boyfriend, on June 8 my period came and lasted 3 days and was light. While on my period I had sex with a old friend and used a condom it didn't break but it came off inside most of the sperm dripped out, I am now pregnant, and want to find out if the likely hood of it being while I was on my period ?