How easy is it to get pregnant?

so my boyfriend and I are both virgins, we're older but we're going to the beach, just an over night trip. we're planning to have sex, but as much as i love him, im worried that i'll get pregnant. hes buying the condoms & he doesnt *** right away, which is good, but im not on birth control, and even if i were to get it, our trip is in a couple days so it wouldnt really kick in. i wanna know how much of a risk it is if we just use a condom. do they break easily or what? bc he isnt smalll at all. but he should know what to get, condom wise.