How do i convince my boyfriend to get tested?

its been 8 months with my boyfriend, he has a big ego. i talked to him about getting tested and he totally rejected the idea. we've gotten into numerous arguements over me convincing him to get tested with me, but hell always say, "hell no, im not gonna get tested!", "i know im not sick", this is really getting me concerned, because now im starting to think that he might be infected with something and is hiding it. what should i do to?