Bactrim and STD

Hello Doctor, My question is...I was put on the antibiotic Bactrim 3 days ago and on the same day I recieved unprotected oral sex from a female (Massage Parlor)...I am worried sick over this mistake I have made and cant sleep for fear I may have got something...I have no symptoms that I read about on your site but could the bactrim slow down, speed up or even prevent any of the STDs you can get from oral sex? I read the chances are very low to get something from oral sex but I am still scared...how long would it be for me to experience symptoms if the bactrim does slow things down? thanks for any advice you provide.