Welcome back to the forum.
I'm puzzled by your exposure history -- unless by chance you happened to pick a user name already chosen by another forum participant (
http://www.medhelp.org/posts/STDs/Concerned-over-exposure/show/1333661). That thread suggests you also had an oral-only exposure to a sex worker in Thailand somewhere between your ex-partner event in early August and start of your new relationship more recently. As we discussed there, it was unlikely you would have acquired any STD during the oral-only event, especially chlamydia.
Based on the information in this thread, it simply is not possible to tell whether your chlamydial infection was acquired from your ex or new partner -- but it clearly was one of those, i.e. not from the oral-only event. The main chlamydia symptom in men is discharge of cloudy fluid from the penis, often small in amount and easy to miss, with or without mild discomfort on urination. Usually symptoms start 7-14 days after catching the infection. Probably about half of all men with chlamydia don't get symptoms at all. So you could just as easily have an infection since early August versus picking it up from your new partner. (But I can't tell from your previous thread whether you had a negative test result somewhere between early August and now -- in which case, your infection came from your new partner, not your ex.)
If you caught the infection from your new partner, then obviously she is infected; and if you had it before, you exposed her. Either way, she definitely needs to be treated, and ideally should also be tested. But she must be treated even if her test is negative. Your ex-partner also needs to be informed and treated, if there was no negative chlamydia test after your last sex with her.
I hope this helps. Regards-- HHH, MD