Seeking pregnancy help

Hi there! I'm in a serious relationship with the most amazing man who has a 14 month old son. We have talked lots and really want to start a family in the near future. I really am considering getting pregnant without him knowing... Like I'm not being bad but I'm currently on birth control pills and we pull out most of the time. I wanna try to plan the right time to get pregnant without us just banging all the time unprotected. If we get pregnant I want him to be surprised rather than disappointed if it doesn't happen