Chlamydia is not a virus, it's a bacterium. Technically, it can be transmitted through oral sex, but it would be extremely abnormal. There are a lot of expert that say it is not possible to get this infection through oral sex.
So if you had any other sexual intercourse maybe the reason is there.
Oral sex exposes you to syphilis and gonorrhea specially. You can also get herpes but you would have seen the lesions on the skin, so you wouldn't have touched her vagina.
It would be interesting to test for gonorrhea after 3 weeks and for syphilis after 6 weeks. If you get a negative result for syphilis, it would be good to test again after 3 months, as there are people that take longer to show a positive result.
You can also test for herpes after 3 months.
All the best.
Dragon.