So me and my boyfriend are planning on having sex soon

Need advice!! We are gonna use the trojan magnum condoms and a sponge for myself with lube any advice? I really don't wanna get pregnant so I'm praying everything goes well. I'm gonna have sex 6 days after my fertile window should I take a ovulation test to be sure I don't have sex when I'm ovulating. I know sperm or precum can live in the body for 5-6 days any advice? Please help I really wanna prevent pregnancy .