How likely is it to get pregnant using the withdrawal method?

I'm not on any BC all we use is the withdrawal method,we don't have sex all that often! I know you can get pregnant and if it was to happen we would be blessed but we are not actually trying right now. How many of you got pregnant by it? I heard pre-cum don't have any sperm in it unless we ejaculated before you had sex. Me and my husband just go straight to sex,he don't ejaculate before. So is it likely for me to get pregnant? I had sex on my fertile day using the withdrawal method and it was a 15% chance day :)