What bacterial infections could I contract by having unprotected anal sex first following vaginal sex? I always get tested for STDs and HIV whenever I have my annual pap smear as a safety precaution. In previous years, my results came out negative for al

A . A yeast infection or bacterial infection would not give you a false positive chlamydia result. If your chlamydia test was negative last year and positive this year then you contracted it in the past year. To answer the other part of your question, the same std's you can get from vaginal intercourse are the same for anal, howeve you could have a higher chance of bacterial vaginosis since you are introducing bacteria from the rectum into the vagina. Lastly, please use condoms to protect yourself against std's. All the best.