PLEASE HELP: pregnancy scare

18 m 😭 im so scared me and mygf had our first experience. We got carried away and did the deed. I want to know what are the chances I get someone pregnant if I used withdrawal method. It did not even went it only the tip but im scared the pre cum will get her pregnant. I ej@cûlated 20 seconds after i told her to get off. Im so dumb i should have waited until I got condoms.

please i need urgent help because its all i think about now. My gf not worried but i ammmm. I genuinely do not know the answer