I'm numb

So I got a call back from the nurse, where I go get check come to find out I have chlamydia. I've only been with 1 person for 3 years. And he says he hasn't slept with anyone I don't believe him. I wish he could of been honest. Am I wrong for not wanting to be with him anymore. Even though it's not easy to get a divorce. I really need someone or at least some advice. I don't know how to feel.