Some how chlamydia “popped” up in my relationship. He hadn’t been with anyone in more than a year and all of my STD test were negative in April and i haven’t been with anyone else since then. How could chlamydia all of a sudden appear?

I have got an appointment for tomorrow and I am really nervous and VERY embarrassed will the doctor examine me or will I just be able to have a prescription for antibiotics? Also I feel as though I am in the wrong as I am only young and would be very embarrassed to be examined as I smell bad and that’s why I’m going to the doctors? Any friendly advice thank you . Also I know I do not have an STD. Thank you