Really weird question need HELP!!!! lol?

k at my first prenatal appointment i was tested for stds like im sure every one is well it came back that i had chlamydia the first person i told was my bff she said that when she was pregnant she was told she had it to but her boyfriend didn't and i thought that was weird my boyfriend got tested and his results came back a few days ago and he didn't have it i was just wondering if its possible that girls get something like it when they get pregnant my mother in law also had this happen to her has this happened to anyone else its really important that i find answers to this because we haven't slept together sense we found out i was pregnant and he thinks im cheating on him