My husband and i have never had any other sexual partners, but my last pap smear showed hpv. further testing showed hpv-16. how is this possible?

Stop worrying: I'm not satisfied that even the "bad" strains of hpv are always transmitted sexually. And this is not a helpful line of inquiry. You love one another, and have promised to be together for the rest of your lives. Don't let this be a cause of suspicion, and remain vigilant for the cancer risk to you both, and things will be good. I wish more people would save themselves for that one special person.