Will my gf get pregant even i eject outside and continue the

I had sex with my gf , and i eject outside . but i am really worried if my gf will get pregant , cause i don't use condom and there might be some sperm inside her vagina , but just very little and also i did not went deep into her vagina , more on the lower part of the vagina..

so please i need help . is there any medicine that wld prevent the egg from fertilize?