Condoms

Im a little worried about using condoms as a sole method of birth control because of all the horror stories and the fact that efficiency drops to 80 something percent when accounting for “human error” but I’ve also heard of people using them as effective birth control for years and years so how well have they worked for you all and what is the human error they mean? Using the wrong size? I dont want to put hormones or copper in my body if i dont have to leaving condoms as pretty much my only option btw.