actually you don't have to be having anal sex to have std's there - especially not herpes or hpv.
grace
I will bet you anything you never had chlamydia.
Why do you think you have rectal pains? If you've had anal sex, then its something worth worrying about. If not, it has nothing to do with STDs.
I have no idea why you were told you had chlamydia if you had consistently negative tests. I'd certainly question how your provider came to that conclusion despite all those negative tests saying otherwise.
have you been tested for herpes yet to know your status?
you can also have viral infections that can cause urination issues and they take time to run their course. you also can have hormonal issues that cause urinary spasms that can be mistaken for urethritis too. if your urine testing is consistently negative, odds are it is something non-bacterial going on.
An urogynecologist is often helpful with issues like this. They cover us gals completely down yonder and often think a little differently from a regular gyn and a regular urologist. might be worth a follow up.
grace