What is the chance of pregnancy when sex takes place 2 or 4 days prior to ovulation?

I just went off the pill 2 months ago, and I’m supposed to get an IUD next month. For the 2 months between my boyfriend and I have been relying on condoms, but one of them broke early Wednesday morning. I think I may have ovulated between Friday and Sunday. What are the chances that pregnancy will occur?

gameorruss