Chlamydia Help

Here is what happened. After about 6 months of being together with my
girlfriend I contracted chlamydia, she had no signs or symptoms of it.
We both went and seen our doctors and were prescribed the correct meds
and everything has been fine since.

Question is was she with another person just prior to her infecting
me, or was it just a case of her being asymptomatic and me contracting
it 6 months after we met?  If the later is true, then why did I not
contract it sooner than 6 months into the relationship?  From reading
up on chlamydia, it appears to me that the male will show signs 7-21
days after being infected. If in fact that is the case, then she had
to be with another person just prior to me contracting it, would this
be right?

I guess what i'm asking, has there been another person she has slept
with since her and I met 6 months ago?

Your information would be greatly appreciated.  Thank You