pregnant from pre cum

Erica
So me & my boyfriend didn't have sex but I rubbed my (TMI) vagina Against the tip of his penis. We had NO penetration whatsoever & the last time he came was about 3-4 weeks ago & it wasn't with me. I'm not in my fertile days (that was last week) & im expecting my period next week. So what's the percentage of me getting pregnant from pre cum?