Suggest Treatment For Burning Sensation While Urinating

This is an std/ sti question. My gf was raped when she was younger like 7 by a man who later died aids. She told me all she got was clymidia from him and was cured. Ive been sexually active with her for months and recently my penis burns when i pee, and also my urethra itches from time to time. I sometimes find black lint on the tip of my penis, i think its from my jeans but im not too sure. so what should i do? do i have anything?