Dear Welcome to HCM We understand your concerns I went through your description. Your worries re unwarranted for. Though you had chances of contracting STDs after having unprotected sex, your doctor said there is nothing wrong. Masturbation is not a sin. The whitish thing you are mentioning inside your foreskin could possibly be a mixture of semen, urine, dust particles and other impurities. Wash it and it goes away. Your worries are allayed till you see the same again after two or three days. Therefore, keep your private area alwaysy clean and be hygienic. You might need psychological counseling. You can contact me through www.healthcaremagic.com customer care officers for telephone counseling. Hope this answers your query. Availble for further clarifications.