I have an intercourse triggered chronic pain in the perineum and reasons to believe there is an infection.
Did a doctor gave you the diagnosis of an infection? Did he performed a culture?
There are other more simple causes of genital and perineal pain not related to infectious disease. I doubt that you have seen a doctor. Better make an appointment to be checked.
Is Chlamydia the only bacteria susceptible to cause a genital infection?
No is not the only bacterial cause of infection, there is a huge number of pathogens that can cause genital al perneal area diseases. They range from common normal flora infections, to contagious STD´s. Chlamydia mostly cause infection out of sight, like in the cervix.
Can't an infection be triggered by a factor other than a bacteria?!
If you are a female, yes infections can be caused aby i big number of factors like change in hormonal rythm, bad hygiene, alterations of the normal vaginal flora, etc.
In males it can also happen espontaneously, more frequently in non circumsized males. But is not as common as with females.
Do an appointment to a trustable doctor. Stop guessing.