Hi it me... confused

I just got tested positive for chlamydia a couple days ago but my ex went to the doctor maybe a week or two ago... at least that’s what he told me & tested negative for all STIs and STDs & since his doctor visit he was the only one I’ve messed with but maybe 2/3 weeks before I did mess with someone else, he used a condom but he did give me oral sex... I didn’t kiss him or give him oral sex. Ik chlamydia could come from just oral sex BUT........ He is also showing me records that he doesn’t have chlamydia. I have not messed with anyone but them since my last last doctor visit in November :/ and now I have chlamydia and idk who to believe tbh or what to do other than tell my ex but who did I get it from fr.

Edit: thank you guys, it was my ex... he’s results actually never cleared about chlamydia, they only had on record STD checks as negative and chlamydia was NR... so we go in today to get his pills. It’s just frustrating cause if it’s not one thing, it’s another with us... we don’t want a struggle love but right person, wrong time.