Birth control + natural family planning

Does anyone here do this? I asked my family planning doctor if I can do it, she said yes if it makes you feel better, though the copper coil kills the sperm as well as the EGG so they don't have chance to meet in one piece. OK, that makes me feel better. But I still think I'd like to avoid my fertile period for peace of mind. So what times of the month is it okay for my boyfriend to cum inside me vs pull out (imagine for a mo I wasn't on birth control, what would you say?)... Thanks.