Pre cum

So until my husband gets a vasectomy, we use the withdrawal method or condoms. I was ovulating yesterday and we had sex. He pulled out in time, but I worry about sperm in precum. From what I’ve read, precum is fluid that comes from glands inside the penis, but do not contain sperm. If a man ejaculated prior to vaginal intercourse, there can be left over sperm in the urethra. When the precum fluid leaks out of the penis, it can then contain residual sperm. My husband had not previously ejaculated, but I read today where some men constantly leak sperm even before ejaculation during intercourse and I’m a little nervous about pregnancy. We’ve had three kids and are done. I’ve tried several types of birth control methods like pills, patch, ring etc., and the hormones do not agree with me—even low dose bc. Pregnancy for the fourth time does not agree with me either however, so that’s why my husband is getting a vasectomy, but until then, like I said before, the methods I mentioned have been our ways of preventing pregnancy. I’ve always tried to avoid sex on my ovulation days too, but yesterday it was just one of those moments. Have any of you gotten pregnant by the withdrawal or pull-out method?