I hope no-one would laugh at your Question, but you seriously need to think about your contraception issues.
Remember, intercourse is a biological function, and the aim is conception, so nature has weighed the odds seriously in favour of this result.
Want to know the odds you are dealing with?
If every sperm in the average ejaclutatin fertilised an egg, you could double the population of North America - that's the USA and Canada, the second largest country in the world - combined!
And it only takes one sperm to do it's job.
Those are the odds, do the maths - get some method of contraception sorted - and no, withdrawal is not secure, it is possible to release sperm before ejaculation.