How effective is pull out method? How likely are you to get prego from precum?

Lane

First of all, I am supposed to start birth control after my next period and we usually use condoms but there have been (more than) a few times where we ran out, and just pulled out. Saying this because I realize "pull out is not birth control".. Dont need any rants, I am an adult and can handle the consequences. However, would like some advice. I made sure to use a dome when i was ovulating. About a week ago I got what I thought was an early period, but it was mostly brown until the end when it returned to the normal red, and super light. Only lasted 2 days. Ive read about implantation bleeding but I didnt think the timeline matched up (we didnt have sex for more than a few days leading up to this). Anyway, now i am 2 days out from my projected period, and I havent had any of my usual indicators that its coming up. But im not experiencing pregnancy symptoms either, besides a little bit of stomach weight, but ive been eating not great so maybe im paranoid? Sorry for the lengthy post- wanted to share the details. I know my best bet is a test. Just wondering if anyone could tell me how likely you are to get pregnant from precum? And is the pull out method really that ineffective?