Chlamydia

I tested positive for Chlamydia & my boyfriend claims he didn’t cheat on me I’ve been tested before I met him and after I’ve been wit him I always get tested my ob said he had to of been with someone else he swears he didn’t cheat on me idk what to do or who to believe like obviously my doctors are certified & he’s not so like ... yay 20 weeks pregnant might’ve gotten cheated on