Hi, Thanks for your query. Unprotected sex makes you vulnerable to STDs and STD symptoms whether you are straight or gay, married or single. There are number of sexually transmitted diseases that can affect men and some of them are mentioned below with their symptoms- have a look! Chlamydia: This bacterial infection affects genital tract and causes symptoms like painful urination, testicular pain and discharge from penis etc. Gonorrhea is another STD in men with symptoms like painful bowel movement, anal itching, thick cloudy or bloody discharge from penis and painful swollen testicles. Trichomoniasis is another common STI caused by one-celled parasite known as trichomonas vaginalis. It infects the urinary tract in men and shows symptoms like discharge from penis, pain during intercourse, itching or irritation inside the penis and painful urination. HIV: This infection is a life-threatening disease which causes number of symptoms in men. These symptoms include fever, headache, rashes, sore throat and diarrhea.