<s>[INST] I was just prescribed doxycycline and metronidazole for a bacterial infection that I received sexually.  I would like to know what caused this?  Does this mean that the guy that I was with has been with someone else or did he need to wash or take a bath before he was with me?  I want to know if I need to stay away from this guy because he may be having sex  with someone else that has a bacterial?   No one has explained the causes to me and I would like to know to avoid this from happening again please. [/INST] Hello, Welcome to Chat Doctor, There are some good microorganisms in the genitals whenever there are alterations in the genital environment these bacteria will activate and produces the symptoms which you are having. There are many sexually transmitted infections which will produces these symptoms, I would suggest you to undergo physical examination to find out whether there is any STIs. STIs is confirmed by physical examination and lab investigations, both the partners should examine and evaluated to confirm the presence of STIs. Thank you. </s>