Wart on my gum?

I've posted a few times about this white spot on my gum that I wasn't sure if it was an abscess or not. I seen my dentist today and she said it looked like a wart from HPV. If that's what it is, how did I get it? I know HPV is a sexually transmitted disease. I've only been with my husband the past 16 years and he's only been with me. I have pap smears every year or two. They never mentioned I've got anything. I'm so confused as to how I got it. I also don't give oral sex to my husband. Ideas?