Ladies, can you answer this question for me?

So my man and I use spermicide during sex instead of condoms.

We usually go without it for like a minute, and then insert the spermicide for the rest of the way.

Yesterday was my ovulation day. We had sex twice, exactly the way I just described. What are the chances of getting pregnant from precum on your ovulation day?

I know pregnancy from precum is rare, but not impossible, and pregnancy from sex while ovulating is high, so I'm just trying to figure out the probability and see if we should be more careful?