The thing about the pull out method is that it is more effective than no birth control, but there is a risk even if the man pulls out every time before he ejaculates because there can be sperm in his pre-cum, and therefore it could get into your body before he ever ejaculates. So it's not just that he might not pull out, but even if he does you can still get pregnant.
Of course, it would be hard, but possible. I am surprised that you have been doing this successfully for five years!!
Not that it is a bad thing to do, but if you really aren't ready for kids, the risk isn't really worth it.