STI Confusion

I've recently found out I have Chlamydia, which I've treated with Antibiotics. I told my sexual parent I last has been with but he says he's been tested about two weeks ago and he's clean. If we DIDN'T use a condom is it possible he didn't get it? I'm 98% sure he gave it to me as I haven't slept with anyone since him and if I had it before I've slept with him I would have passed the infection onto him?