STDs and relationships

So I went to the doctor yesterday and they always do a chlamydia test. Well, it was positive. I feel absolutely disgusting and embarrassed. I asked my boyfriend if he cheated on me he said no, that he probably got it from his ex back in November. We started having sex in March. Our relationship has been a little rocky lately and I guess I’m just curious if this is a good enough reason to leave. He doesn’t think it’s a big deal.