Over the course of our marriage, my husband and I had regular unprotected sex 3-4 times a week during all the times I was not fertile. Then when we were not trying, we used pullout. I have always been quite fortunate and had a pretty regular cycle so it was easy to manage this and we never got preggo accidentally (except for when we were taking chances we shouldn't have been.)
With my first son, he was an oopsie and only had unprotected sex 2x the day or two after my period ended but I ended up ovulating early and got pregnant, had to be a pretty long cutoff, at least 3 days because I'd just gotten off my period but at the same time I was not tracking ovulation in those days, just not having sex in the middle of the cycle, so I can't 100% say for sure how many days it was.
With my second son, we were trying but my husband changed his mind so we stopped BD, we thought in plenty of time, but again I did get pregnant and with at least 3 days' cutoff. I was much more savvy about my cycle then and we had definitely stopped BD 3-4 days before I ovulated.
With my third son, we were trying for Shettles cutoff and so we BD a few times and then my husband had to leave and I ovulated when he wasn't even at home LOL. Again, a cutoff 2-3 days and again, we had absolutely stopped BD 2-3 days before I ovulated.
With my 4th, I wasn't ovulating regularly due to breastfeeding and so we were just having unprotected sex regularly. I honestly do not know when I got him in relation to ovulation because I was not having my period, but I do remember having a few unprotected attempts.