I am five months post partum with my first. (Hopefully only for a bit!) I went on the mini pill six…

I am five months post partum with my first. (Hopefully only for a bit!) I went on the mini pill six weeks post partum and have had really irregular bleeding and was gaining weight like crazy so I decided it was in my best interest to stop taking it. Two days later my SO and I had sex and the condom came off while inside me! I eventually did get it out but we are unsure if he came in the condom or if it was off way before! I immediately ran to the store for plan b. I know you are extremely fertile after you have a kid but is there still a BIG chance I might get pregnant?