I have very important question about pre-cum

so straight to the point... um he was inside of me for like 30 seconds. but i stopped him bc he didnt have a condom on. he is clean so im ok on the std front, i am still getting checked out obviously. but what im worried about is the chance that one can become pregnant because of pre cum. he did not get off inside of me(i mean really 30 sec, who could...) but im still just wondering...