HELP !!

So this is kinda gross I guess but I need help. I’ve been dating this guy for about 6 months now and about a month ago he took my virginity. Everything has been great !! Im moving in with him in 2 weeks. Problem is, I just found out I have Chlamydia. Obviously it came from him as he was my first. He told me there was a girl he had a one nighter with before he got with me, about 9-10 months ago. The doctor said this was completely possible. But my moms been saying he may he cheated, yadayadayada. What do you guys think ?? Did he cheat ? I asked and he said no. He’s never lied to me before.