combining contraceptives

so the pill isn’t an option for me. i’ve been feeling my cervical position regularly to see if it’s low and firm (not ovulating) and only have sex when it is. we also use condoms and he pulls out every time we have sex. we also check the condoms for holes. i feel like our only risk is possibly precum being transferred when putting the condom on but i’m not sure what the chances of that are. am i too worried? or is this not effective enough at preventing pregnancy?